Start of the VSCode extension README

[dotNomad]

This PR adds the start of the VSCode extension README that is bundled with the extension, and shown in the VSCode Marketplace.

Intent

Resolves #1685

Type of Change

• • [ ] Bug Fix
• • [x] New Feature
• • [ ] Breaking Change
• • [x] Documentation
• • [ ] Refactor
• • [ ] Tooling

Approach

Some extensions referenced:

• https://github.com/quarto-dev/quarto/blob/main/apps/vscode/README.md
• https://github.com/gitkraken/vscode-gitlens/blob/main/README.md
• https://github.com/prettier/prettier-vscode/blob/main/README.md
• https://github.com/tailwindlabs/tailwindcss-intellisense/blob/master/packages/vscode-tailwindcss/README.md

[dotNomad]

Marking this as ready to review. I plan to add some more, but I can do it as a follow-up if this gets merged.

If anyone has bits they think should be added feel free to comment