Add select-mode, version, pack and publish sub-actions (#656)

* Add select-mode, version, and publish sub-actions

* Rename

* No github-token needed for select-mode for now

* extend select-mode with publish-plan check and upload

* Rename base-branch to pr-base-branch

* add `pack` subaction

* `--from-pack` support in the publish subaction

* rename CLI arg

* update rolldown config

* rename pack dir input/output

* tweak retendion days

---------

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

publish/README.md

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+# changesets/action/publish
+
+TODO

publish/action.yml

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+name: Changesets - Publish
+description: Publish packages to npm
+runs:
+  using: node24
+  main: ../dist/publish.js
+inputs:
+  github-token:
+    description: "The GitHub token to use for authentication. Defaults to the GitHub-provided token."
+    required: false
+    default: ${{ github.token }}
+  script:
+    description: "The command to use to publish packages"
+    required: false
+  pack-dir-artifact-id:
+    description: "Artifact id for packed publish output generated by the pack subaction"
+    required: false
+  create-github-releases:
+    description: "Whether to create Github releases after publish"
+    required: false
+    default: true
+outputs:
+  published:
+    description: "A boolean value to indicate whether a publishing has happened or not"
+  published-packages:
+    description: >
+      A JSON array to present the published packages. The format is `[{"name": "@xx/xx", "version": "1.2.0"}, {"name": "@xx/xy", "version": "0.8.9"}]`
+branding:
+  icon: package
+  color: blue