feat: initial v3 plugin impl

[snorrees]

@SimeonGriggs does the updates to README / API look ok to you? Do you know if people have hundreds of languages with this? Might make me roll back selected-langs-in-url change.

@mariuslundgard FYI, review if you want to. -I kept your store-langs-in-url-state, as it seemed useful.-

Edit: Will replace url-state with localstorage again, because "I think the intention is that like a “german content editor” would only ever always want to see the german content on and all others off", which does not work well with url state."

Will merge this and publish using the workflow and make the repo public when done.

How to test

npm i @sanity/language-filter@first-pass

Follow the install readme

This is also a test if doing a branch-prerelease with semver is a good idea ;)

[github-actions[bot]]

:tada: This PR is included in version 1.0.0-v3-studio.1 :tada:

The release is available on:

• npm package (@studio-v3 dist-tag)
• GitHub release

Your semantic-release bot :package::rocket:

[github-actions[bot]]

:tada: This PR is included in version 3.0.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: