write docs for setting up VSCode ESLint plugin to work with gts/gjs files.

[hmajoros]

in order to actually see eslint errors/warnings in gjs/gts files, I needed to add the following to my VSCode settings:

    "eslint.probe": [
       // ...
       "glimmer-js", 
       "glimmer-ts"
     ],
    "eslint.validate": [
      // ...
      "glimmer-js",
      "glimmer-ts"
    ],

I didn't see this documented anywhere, and want to create a ticket to make sure this gets documented somewhere. I am open to ideas on the best place for these docs to live. Presumably we should note this in the glint docs & the eslint-plugin-ember docs, but also probably here, since this seems like the home of any thing template-imports related.

[NullVoxPopuli]

any chance you'd be willing to PR to the README?