ci: libs publishing workflow

[asvishnyakov]

Closes #2550

This PR enables automatic publishing of the @chainlit/react-client (and any other non-private package in libs/* if we will add them) to the npm registry.

To test the publishing process, use the Dry run (test publishing) option, similar to the Publish to TestPyPI instead of PyPI feature introduced in #2483.

Other changes:

• Removed pnpm install arguments, since CI must always use a frozen lockfile.
  • Updating the lockfile during CI runs is bad practice, as changes are not committed back to the repository and resolved dependency versions may differ from those declared in the source code.
  • If you encounter an error where pnpm indicates that the lockfile needs to be updated, run pnpm install or pnpm install --lockfile-only locally and commit the resulting changes to the PR where the CI failure occurred.
• Removed pnpm-skip-install from pnpm-node-install action since no longer used anywhere
• CI will be skipped if the PR or commit includes only markdown files located at the repository root or the LICENSE file.