[jsonp-dev] Rename master branch to main

[Mark Swatosh <mark.swatosh@xxxxxxxxx>]

Hi all,

I opened a PR in the eclipsefdn repo to have the JSON-P master branch renamed to main as requested for the 2.2 M1 release: https://github.com/jakartaee/.eclipsefdn/pull/21

Given the spec hasn't had any commits in the last year this seems as good a time as any to make this change, but if anyone thinks we should hold off for some reason, let me know or respond in the PR.

The existing jsonp-api PRs should automatically retarget the main branch after the change, but local environments will need to be updated.

Thanks,

Mark