Update prep for 4.0.0 beta

[hardillb]

• [x] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)

Proposed changes

• Update NodeJS versions for 4.0.0
• Update README.md
• Make healthcheck match across all builds
• Update GH Action versions

Checklist

• [x] I have read the contribution guidelines
• [ ] For non-bugfix PRs, I have discussed this change on the mailing list/slack team.
• [ ] I have run grunt to verify the unit tests pass
• [ ] I have added suitable unit tests to cover the new/changed functionality

[dceejay]

looks good :-)

[knolleary]

Node 22 isn't due until April 2024 - I would hope we have Node-RED 4 beta available long before that. Does it need removing from this PR for now? We can always add 22 later once it is available.

[hardillb]

Yep, I'll update the base branch

[hardillb]

@knolleary should be good now

[hardillb]

Merging