chore: Update comments in launch.json (Azure#4303)

I was talking with Marina today about my workflow for debugging
changes in `azd`. I use the "Debug azd cli" launch configuration for
most of my debugging and end up modifying `launch.json` to set the
`cwd` and other parameters for the profile for the specific end to end
I want to debug.  There are some `git` tricks that you can play to
ignore modifications to this file (so you don't have to worry about
checking them in).  I had documented them in one place but not the
other (since I typically run VS Code from within the `cli/azd` sub
folder, to have a smaller workspace) and didn't document how you undo
this behavior.

This patch updates the comments to show how to turn this off, and adds
them to our root `launch.json` as well.

.vscode/launch.json

@@ -2,6 +2,11 @@
     // Use IntelliSense to learn about possible attributes.
     // Hover to view descriptions of existing attributes.
     // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+
+    // You can run `git update-index --skip-worktree .vscode/launch.json` to have git
+    // ignore changes to this file so you don't need to worry about commiting your edits. If you ever
+    // need to merge this file afterwards, you'll need to run `git update-index --no-skip-worktree .vscode/launch.json`
+    // to ensure git tracks changes to this file again.
     "version": "0.2.0",
     "configurations": [
         // If you set `AZD_DEBUG=true` in your environment, `azd` will pause early in start up and allow you to attach

cli/azd/.vscode/launch.json

@@ -1,6 +1,8 @@
 {
-    // You can run `git update-index --skip-worktree .vscode/launch.json to have git
-    // ignore changes to this file so you don't need to worry about commiting your edits.
+    // You can run `git update-index --skip-worktree .vscode/launch.json` to have git
+    // ignore changes to this file so you don't need to worry about commiting your edits. If you ever
+    // need to merge this file afterwards, you'll need to run `git update-index --no-skip-worktree .vscode/launch.json`
+    // to ensure git tracks changes to this file again.
     "version": "0.2.0",
     "configurations": [
         // This will launch azd (starting from main.go), under the debugger.