Small changes for gitpod / VS Code integration

Add subprojects/ to the .gitignore.
Open the welcome message in the editor.
Fix a typo in the welcome message.

Author: setton

.gitignore

@@ -99,3 +99,6 @@ integration/vscode/ada/linux/
 
 # GNAT Studio clangd options
 .clang-format
+
+# Subprojects
+subprojects/

.gitpod.yml

@@ -10,7 +10,7 @@ tasks:
       git -C subprojects clone https://github.com/AdaCore/VSS.git
       git -C subprojects clone https://github.com/AdaCore/spawn.git
       git -C subprojects clone https://github.com/AdaCore/libadalang-tools.git
-      gp open doc/gitpod.md
+      code doc/gitpod.md
       echo make LIBRARY_TYPE=static
 
 vscode:

doc/gitpod.md

@@ -16,7 +16,7 @@ In a gidpod session you can:
   menu
 * start debugger with `/Debug/Start Debugging` menu (or `F5`)
 
-The aditor has a lot of commands build in. Press `F1` to search a command.
+The editor has a lot of commands built in. Press `F1` to search a command.
 
 By default the editor is configured for the `gnat/lsp_server.gpr` project.
 You can switch the project by changing `/File/Settings/Open Preferences` or