Update release docs for VSCode extension versions

[dotNomad]

This PR updates the release instructions in our CONTRIBUTING.md guide to reflect our version number for the VSCode extension.

It is based on the VSCode recommendations found here: https://code.visualstudio.com/api/working-with-extensions/publishing-extension#prerelease-extensions

Intent

Resolves #1868

Type of Change

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