I spent a couple hours this morning creating the extension. I've never made one before and it was pretty fun!
I've published it on the marketplace too! (Its called 'WhatFile')
The README has what you need to set in your settings.
It was surprisingly easy to write this, it was more of a challenge to upload it
If you wanna write an extension I'd recommend looking at: https://code.visualstudio.com/api/get-started/your-first-extension