Update FDC3 master branch to main

[Julia-Ritter]

Description:

The FDC3 team would like to rename the repo master branch to main.

Items

• Agree on this list of tasks as the plan to move forward
• Prepare a PR with name replacement across the entire codebase; this includes, but is not limited, to links and GitHub actions; this is a good start - https://github.com/search?q=repo%3Afinos%2FFDC3%20master&type=code
• Choose a target date for merging
• Notify community
• Rename the branch and merge the PR
• Post-migration check for broken links

[maoo]

@kriswest - happy to support this! I took the freedom to rewrite title and description of the issue; WDYT?

cc @robmoffat @TheJuanAndOnly99

[kriswest]

LGTM, that search is revealing more links than I thought there were, so good start!

I'd include doing a post-migration check for broken links at the end of the steps. I think docusaurus does its own link checking and will report build errors if they're found, but we may also want to run a 3rd party tool - neither will find anything until after the branch rename of course.

[TheJuanAndOnly99]

PR is ready #1161.

[kriswest]

Merged and completed!