It's election day and I can't focus on complicated tasks today, so I'm investing some time in tidy-up work instead.

This pull request attempts to clean up some of the settings descriptions for the extension:

• Uses markdownDescription where appropriate to add hyperlinks and code fences
• Replaces "folder" with "directory"; "application" with "app" per Google developer style guide
• A few minor grammar nits or clarifications where I believed they improved the text

I've tested this locally by running in the extension development host to make sure the changes are presented correctly in launch.json and the settings editor.