docs(Edge): Document setup for Chromium-based Edge

In a comment from April 2020 [1], the Selenium maintainers said that
they would not support Chromium-based Edge in Selenium 3.  They
instead suggested waiting for a stable version of Selenium 4.
However, as of December 2020, there is no release date in sight for
Selenium 4, Chromium-based Edge is the only version of Edge actively
supported by Microsoft since August 2020, and legacy Edge will reach
end-of-life status in March 2021 [2].

Thankfully, Generic WebDriver Server is generic enough to handle this
case.  We can use it to configure Selenium 3 to respond to Edge and
use Microsoft's `msedgedriver.exe` as a backend executable.

See also SeleniumHQ/selenium#8993

[1]: SeleniumHQ/selenium#8237 (comment)
[2]: https://techcommunity.microsoft.com/t5/microsoft-365-blog/microsoft-365-apps-say-farewell-to-internet-explorer-11-and/ba-p/1591666

Author: joeyparrish

Edgium.md

@@ -0,0 +1,82 @@
+# Generic WebDriver Setup for Chromium-based Edge
+
+In a [comment from April
+2020](https://github.com/SeleniumHQ/selenium/issues/8237#issuecomment-629851734),
+the Selenium maintainers said that they would not support Chromium-based Edge in
+Selenium 3.  They instead suggested waiting for a stable version of Selenium 4.
+However, as of December 2020, there is no release date in sight for Selenium 4,
+Chromium-based Edge is the only version of Edge actively supported by Microsoft
+since August 2020, and [legacy Edge will reach end-of-life status in March 2021.](https://techcommunity.microsoft.com/t5/microsoft-365-blog/microsoft-365-apps-say-farewell-to-internet-explorer-11-and/ba-p/1591666)
+
+Thankfully, Generic WebDriver Server is generic enough to handle this case.  We
+can use it to configure Selenium 3 to respond to Edge and use Microsoft's
+`msedgedriver.exe` as a backend executable.
+
+If you haven't read
+[setup.md](https://github.com/google/generic-webdriver-server/blob/main/setup.md)
+yet, that is where you will find general information on setting up Generic
+WebDriver Server.  This document will focus on specific setup instructions for
+Chromium-based Edge.
+
+## Setup
+
+*NOTE: Though our custom backends can be configured to respond to arbitrary
+browser names, `msedgedriver.exe` responds only to the browser name `msedge` as
+far as we can tell.  So it is important not to change the browser name in the
+configs below to anything else!*
+
+1. Make sure you have the correct version of `msedgedriver.exe` for your version
+of Edge.  See [Microsoft's instructions to check Edge version and download
+the right driver](https://docs.microsoft.com/en-us/microsoft-edge/webdriver-chromium/?tabs=javascript#install-microsoft-edge-chromium).
+You should have Edge version 75 or later.
+
+
+2. Install GenericWebDriverServer:
+
+```sh
+npm install -g generic-webdriver-server
+```
+
+
+3. Create a node config file like this one as `node_edge.json`:
+
+```json
+{
+  "capabilities": [
+    {
+      "browserName": "msedge",
+      "seleniumProtocol": "WebDriver",
+      "maxInstances": 2
+    }
+  ],
+  "host": "127.0.0.1",
+  "port": 5555,
+  "hub": "http://localhost:4444"
+}
+```
+
+You **must** set the `browserName` field to `"msedge"` exactly.  You may
+customize `maxInstances`, `host`, `port`, and `hub` to your grid setup, and you
+may add additional Selenium node configurations as you see fit.
+
+
+4. Create the following batch file as `start_edge_node.bat`:
+
+```bat
+set NODE_MODULES_PATH="%APPDATA%\npm\node_modules"
+
+java ^
+  -cp "%NODE_MODULES_PATH%"\generic-webdriver-server\GenericWebDriverProvider.jar;"%NODE_MODULES_PATH%"\generic-webdriver-server\selenium-server-standalone-3.141.59.jar ^
+  org.openqa.grid.selenium.GridLauncherV3 ^
+  -role node ^
+  -nodeConfig node_edge.json
+```
+
+You may replace the jar file paths with whatever is appropriate for your system,
+but this should be the right path for many installations of NPM on Windows.
+
+
+5. Launch `start_edge_node.bat` to start the Selenium node for Chromium-based
+Edge, or configure Windows to launch it automatically on startup.  If you have
+some existing system for starting and managing your Selenium nodes, you may run
+the command lines from `start_edge_node.bat` in your own way.

README.md

@@ -39,6 +39,14 @@ Out of the box, we provide backends for:
 In addition, you'll need JAR files from the package [`generic-webdriver-server`](https://www.npmjs.com/package/generic-webdriver-server).
 
 
+## Chromium-based Edge
+
+In addition to the backends we provide, you can also use this generic backend to
+support Chromium-based Edge in Selenium 3, in spite of [Selenium's recent
+decision not to support it directly.](https://github.com/SeleniumHQ/selenium/issues/8237#issuecomment-629851734)
+For details on setup for Chromium-based Edge, see [Edgium.md](https://github.com/google/generic-webdriver-server/blob/main/Edgium.md)
+
+
 ## How it works
 
 See [how-it-works.md](https://github.com/google/generic-webdriver-server/blob/main/how-it-works.md)

setup.md

@@ -30,6 +30,27 @@ the name of the application entry point for Selenium, which we would not have to
 specify when running the typical `java -jar selenium-server-...` command for
 Selenium, but it required when using `-cp`.
 
+*NOTE: On Windows, the classpath separator is a semicolon (`;`), not a colon
+(`:`).*  So on Windows, you would use something like this in bash:
+
+```sh
+java \
+  -cp node_modules/generic-webdriver-server/GenericWebDriverProvider.jar\;node_modules/generic-webdriver-server/selenium-server-standalone-3.141.59.jar \
+  org.openqa.grid.selenium.GridLauncherV3 \
+  -role node \
+  -nodeConfig foo.json
+```
+
+Or this in a batch file:
+
+```bat
+java ^
+  -cp node_modules\generic-webdriver-server\GenericWebDriverProvider.jar;node_modules\generic-webdriver-server\selenium-server-standalone-3.141.59.jar ^
+  org.openqa.grid.selenium.GridLauncherV3 ^
+  -role node ^
+  -nodeConfig foo.json
+```
+
 You also need to configure `GenericWebDriverProvider.jar` with Java system
 properties so it knows which backend to start.  This is done with `-D` arguments
 before the class path and entry point.  For example: