Docs: Fix various bad links

Address issues found by hydra-link-checker in the last CI job:

```
- code:    404
  url:     https://qunitjs.com/browser/callbacks/QUnit.on.md
  parent:  https://qunitjs.com/browser/#browser-support
  error:   Not Found

- code:    404
  url:     https://app.element.io/#/room/#qunitjs_qunit:gitter.im
  parent:  https://qunitjs.com
  error:   Not Found

- code:    404
  url:     https://qunitjs.com/api/intro.md
  parent:  https://qunitjs.com/api/QUnit/
  error:   Not Found

- code:    404
  url:     https://qunitjs.com/api/config/config.md
  parent:  https://qunitjs.com/api/config/storage/
  error:   Not Found
```

build/hydra-config.json

@@ -1,11 +1,13 @@
 {
   "//": [
     "twitter.com broken with redirect-loop",
+    "app.element.io chat rooms render fine but use HTTP 404 for some reason",
     "npmjs.com responds HTTP 429 Too Many Requests too easily",
     ""
   ],
   "exclude_scheme_prefixes": [
     "https://twitter.com/",
+    "https://app.element.io/",
     "https://www.npmjs.com/package/"
   ]
 }

docs/api/QUnit/index.md

@@ -6,4 +6,4 @@ redirect_from:
   - "/QUnit/"
 ---
 
-If you're new to QUnit, check out [Getting Started](../intro.md)!
+If you're new to QUnit, check out [Getting Started](../../intro.md)!

docs/api/config/storage.md

@@ -23,6 +23,6 @@ The Storage object to use for remembering failed tests between runs.
 </tr>
 </table>
 
-This is used to power the [reorder feature](../config.md). In [browser environments](../../browser.md) this will use `sessionStorage` if supported by the browser.
+This is used to power the [reorder feature](./reorder.md). In [browser environments](../../browser.md) this will use `sessionStorage` if supported by the browser.
 
 In Node.js and other non-browser environments, there is no storage object available for this purpose by default. You can attach your own preferred form of persistence between test runs, by assigning an object to `QUnit.config.storage` that implements `getItem`, `setItem` and `removeItem` methods, similar to the [Web Storage API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API).

docs/browser.md

@@ -36,7 +36,7 @@ QUnit releases are standalone and require no runtime dependencies for use in the
 
 This is typically saved as `/test.html` or `/test/index.html` in your project.
 
-The above example loads QUnit from the jQuery CDN. For improved experience during local or offline development, it is recommended to [install or download QUnit](intro.md#download) within your project. Some [integrations](#integrations), like Web Test Runner and Karma, can auto-create the HTML from a list of JS files or glob pattern.
+The above example loads QUnit from the jQuery CDN. For improved experience during local or offline development, it is recommended to [install or download QUnit](./intro.md#download) within your project. Some [integrations](#integrations), like Web Test Runner and Karma, can auto-create the HTML from a list of JS files or glob pattern.
 
 Let's add the following script, which tests an "add" function that adds two numbers together:
 
@@ -131,7 +131,7 @@ QUnit requires no HTML markup in order to run tests. The above "Getting started"
 
 To display test results, the only markup necessary is a `<div>` with `id="qunit"`. Without this, the tests will run with the [HTML Reporter](#html-reporter) disabled.
 
-[Browser automations](#integrations) that run tests for you from the command-line, might enable other reporters or event listeners instead. For example, they might use a TAP reporter, or [`QUnit.on()`](./callbacks/QUnit.on.md) to automatically extract results in a machine-readable way, and use it to set the build status of a continuous integration job (CI).
+[Browser automations](#integrations) that run tests for you from the command-line, might enable other reporters or event listeners instead. For example, they might use a TAP reporter, or [`QUnit.on()`](./api/callbacks/QUnit.on.md) to automatically extract results in a machine-readable way, and use it to set the build status of a continuous integration job (CI).
 
 ## HTML Reporter