Update all the docs

[bluwy]

Tied to changesets/changesets#2196

I completely removed the auth docs and move it to the changesets site (PR above). The content flows better when describing the auth together with setting up the workflow.

Issues:

• closes Output doesn't match the documentation #528

PRs:

• closes List missing outputs in README.md #253
• closes Add undocumented outputs to README #264
• closes Add documentation for hasChangesets and pullRequestNumber #334
• closes docs: update workflow examples action versions #374
• closes Add missing outputs in documentation #499

[changeset-bot]

⚠️ No Changeset found

Latest commit: 1734b9a

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