chore: set up release-please

[mdjermanovic]

Sets up release-please.

The release-please.yml file is copied from the espree repo + I added an npm install step (same as in eslint/js#573)

Additional non-code setup:

• Update organization Actions secrets to give this repository access to NPM_TOKEN, MASTODON_ACCESS_TOKEN and the four TWITTER_* secrets.
• Update repository Actions settings to "Allow GitHub Actions to create and approve pull requests". (this was already enabled!)
• Update npm package settings to "Require two-factor authentication or an automation or granular access token"

Please double-check the release-please.yml file and all non-code setup items.

[nzakas]

LGTM. Just one question.

[mdjermanovic]

Just one question.

I assume it's the same as eslint/eslint-visitor-keys#48 (comment)