Support "Add to Workspace Recommendations"

[mark-wiemer]

Feature Description:

In VS Code, I can view extensions and select "Add to Workspace Recommendations" to quickly add the extension ID to my .vscode/extensions.json file. This is a great QoL feature as extension IDs are often a bit awkward to find otherwise. It also easily ensures I don't accidentally add duplicate values.

Similarly, extensions already added to extensions.json have a "Remove from Workspace Recommendations" context menu item, which feels valuable for completeness.

[tsmaeder]

That sound's like a reasonable addition.