Changed VSCode settings.json to ignore git submodules (#21286)

no issue

- This removes the `casper` and `source` submodules from the VSCode
source control sidebar to simplify the view.
- It also points all of VSCode's `git` commands in the command palette
to the root repository (Ghost), so you don't have to specify which repo
you want to commit to every time.
- With this, you can simply run the "Git commit all" command in VSCode
(and optionally map a keybinding to it), which adds all changed files to
the commit and prompts for a commit message.

.vscode/settings.json

@@ -22,5 +22,6 @@
   },
   "tailwindCSS.experimental.classRegex": [
     ["clsx\\(([^)]*)\\)", "(?:'|\"|`)([^']*)(?:'|\"|`)"]
-  ]
+  ],
+  "git.detectSubmodules": false
 }