chore: automate releases with release-please

[bmish]

This should open up a PR any time there are unreleased changes based on conventional commits. Merging the PR will create the release including publishing on NPM.

Devops:

• I had to setup a granular npm access token with write access to this package only as a github repository secret called NPM_TOKEN.

There were a few mistakes in this PR, see these follow-ups:

• chore: tweak release-please action config #737
• chore: tweak release-please permission #743
• chore: fix release-please permission for provenance generation #750
• docs: changelog formatting #753

Successfully tested with this release:

• https://github.com/bmish/eslint-doc-generator/releases/tag/v2.2.2

Based on:

• chore: add release-please eslint-plugin-eslint-plugin#421
• chore: Set up release-please eslint/generator-eslint#144

References:

• https://github.com/googleapis/release-please