ci: lighten PR validation and change release process

[remi-gelinas]

So, with the initial transfer for #19 out of the way, this PR is intended to make some changes to contribution and the release process, some of them discussed in #20 with @purcell.

Laundry list of changes in this PR:

• CODEOWNERS updated to the nix-community/nix-ts-mode team, and not just myself

• PR title validation removed as a requirement. I do still like the conventional commit spec, and I'd prefer it to unreadable commit messages, but the NO-ISSUE cruft is a real concern. At the very least I'd like to eliminate the NO-ISSUE/issue number requirement but still require conventional spec type.

• With PR title validation removed, automatic versioning doesn't make sense (and never really did with a repo of this size). Automatic versioning actions are replaced with simple release and changelog generation actions caused by version tagging events.

• Enable Dependabot version updating for Github Actions, to keep them up to date

• Deduplicate the lint/test actions to use on trunk after appropriate commits and repoint the status badge in the README to the correct repo

Open questions I have for discussion:

1. How do we want to restrict release tagging? Currently, the action in this PR will generate a changelog and release off of any tag. Obviously anyone in the nix-ts-mode team in theory will have permissions to push whatever tags. Do we want to restrict releasing to tags matching a semantic version (i.e. v.XX.XX.XX) exactly, which would leave room for tags for other uses? Do we really even care given how low traffic this repo is right now?

   EDIT: It occurs to me that we could easily use protected tag patterns for this - protect semver tags for individuals with release permissions, and that should solve the problem rather nicely

2. Looks like other projects in nix-community tend to use Renovate rather than Dependabot - I prefer renovate myself, but did dependabot initially as it's arguably less configuration. Any preference folks have?

[remi-gelinas]

cc @antifuchs and @purcell for comments here :D