feat: adopt changesets + fix exports, bump to 0.4.0

- Install @changesets/cli with fixed mode (all @uncaged/* packages sync version)
- Fix package exports: add bun condition, point import to dist/
- Bump all packages to 0.4.0 via changeset version
- Auto-generated CHANGELOG.md for each package
- Ignore workflow-dashboard (private)
- Add npm scripts: changeset, version, release
- publish.sh: support workspace:^ prefix matching

Closes #241, Closes #242

.changeset/README.md

@@ -0,0 +1,8 @@
+# Changesets
+
+Hello and welcome! This folder has been automatically generated by `@changesets/cli`, a build tool that works
+with multi-package repos, or single-package repos to help you version and publish your code. You can
+find the full documentation for it [in our repository](https://github.com/changesets/changesets).
+
+We have a quick list of common questions to get you started engaging with this project in
+[our documentation](https://github.com/changesets/changesets/blob/main/docs/common-questions.md).