Update all the docs (#703)

* Update all the docs

* Fix heading

pack/README.md

@@ -1,3 +1,31 @@
 # changesets/action/pack
 
-TODO
+This action packs publishable packages into tarballs, complements [changesets/action/publish](../publish/README.md) to publish them in a later step.
+
+## Requirements
+
+- Needs repo checked out and `@changesets/cli` installed
+- [Job permissions][job-permissions]: _none_
+- [Workflow triggers][workflow-triggers]: _any_
+
+## Usage
+
+> [!TIP]
+> Check out [the docs](https://changesets.dev/guide/automating#how-do-i-run-the-version-and-publish-commands) to learn how to set up the version and publish workflow.
+
+## API
+
+<!-- api-start -->
+
+| Inputs                     | Description                                                           |
+| -------------------------- | --------------------------------------------------------------------- |
+| `publish-plan-artifact-id` | Artifact id for a publish plan generated by the select-mode subaction |
+
+| Outputs                | Description                                 |
+| ---------------------- | ------------------------------------------- |
+| `pack-dir-artifact-id` | Artifact id for the packed output directory |
+
+<!-- api-end -->
+
+[job-permissions]: https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#jobsjob_idpermissions
+[workflow-triggers]: https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows