ci(deps): update GitHub actions to run on Node.js 24 (LTS)

[MikeMcC399]

Situation

• GitHub has deprecated the use of node20 and plans to force runners to use node24 beginning on Mar 4, 2026 - see Deprecation of Node 20 on GitHub Actions runners Edit: postponed until June 2, 2026.

• Node.js 20 is planned for end-of-life on April 30, 2026.

• .nvmrc defines Node.js 20 for usage. This will no longer be supported by the end of April 2026.

GitHub Actions workflows are currently based on node20 versions

• main.yml
• publish-on-tag.yml

Change

Update

• .nvmrc to Node.js 24 Active LTS version

Update the above GitHub Actions workflows to use latest node24 versions:

• actions/checkout to actions/checkout@v6
• actions/setup-node to actions/setup-node@v6

[MikeMcC399]

@mathiasbynens

Would you like to review? It just puts CI on a current basis.

[MikeMcC399]

Without this PR, GitHub Actions now warns:

---

build
Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/checkout@v4, actions/setup-node@v4. Actions will be forced to run with Node.js 24 by default starting June 2nd, 2026. Please check if updated versions of these actions are available that support Node.js 24. To opt into Node.js 24 now, set the FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true environment variable on the runner or in your workflow file. Once Node.js 24 becomes the default, you can temporarily opt out by setting ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION=true. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/