Add CI builds for previews

[glenn2223]

Issue

The development of v7 will take some time as the various changes are built up. However, the finished parts should be ready for general release on a preview basis

Proposal

I think we should introduce some CI builds that run each time there is a commit to main. This will mean that these small changes will be generally available and can be used straight away

Notes

As suggested by VS Code docs (as they don't support release suffixes), the preview/CI builds will have odd releases and official releases will be even. CI builds will still have a suffix applied, for internal referencing - it's just going to be dropped by VS Code on the marketplace

I will do my best to ensure that we only increment the release and pre-release versions when new features get added. Fixes should still be applied to the patch releases.

This all means that v7.0.0 and v7.1.0-ci### will be released as a pair (v7 only becoming available when v7.1 is final and we have moved away from v7.1.0-alpha/beta###-ci###)

Changes

• Add GitHub action for CI builds
  • Run it on pushes to main
  • Skip even releases for odd ones
  • Ensure it publishes on odd minor releases
• Update current action to only publish as even minor releases
• Apply doc changes