Upgrade GitHub Actions

[imsys]

Trying to fix these warnings:

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/upload-artifact@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/

[imsys]

Still getting the warning for: windows-mingw and html at https://github.com/nesbox/TIC-80/actions/runs/23028853744?pr=2910

For the html task, it depends on mymindstorm/setup-emsdk#50

For the mingw, it uses msys2/setup-msys or ruby/setup-ruby. Ruby is used in other builds that are not showing the warning, so the problem seems to be from msys2/setup-msys, but I can't say for sure.

I'd say to approve this first, and later we try to fix the missing ones.

[RobLoach]

Emscripten is knowing slow to update to the latest Node.js. If you find their sources, you'll see many issues related to it:
https://github.com/emscripten-core/emsdk/issues?q=is%3Aissue%20state%3Aopen%20node