Automation workflow to build index files on release

[eduard-sukharev]

This PR adds github automation workflow that does following:

• Triggered on pushed new version tag ("v*" regexp)
• Builds index.html.gz files with npm run buildall
• Packs all built files into index_release.zip file
• Creates a new Release based on the pushed tag
• Uploads index_release.zip file to release asset

This workflow allows removing binary blobs of index.html.gz files, which helps reducing git repo size. There will also be no need to build index.html.gz files and committing them by hand. And finally, it uploads the actual valuable release artifacts right into release assets, which should help users locate them easier.

[eduard-sukharev]

Example release with attached release assets: https://github.com/eduard-sukharev/ESP3D-WEBUI/releases/tag/v3.0.0-alpha4

[luc-github]

I already build all packages to test them or let people to test them at almost all commits, because need also to update version which means they are already in dist of Source code (zip) of the release when doing release, and most of commits are not release which means freezing the version for online access is also easy, e.g: https://github.com/luc-github/ESP3D-WEBUI/blob/v3.0.0-alpha3/dist/Printer3D/Marlin-embedded/index.html.gz?raw=true

Adding them as separate zip that need to be unzipped and parsed is not really different than use the already present source zip, I have to build all packages before release because I need to test them - doing a release without testing them is non sense, so building them only at release is in best case redo what is already done, in worst case subject to untested release.

I agree automation is good (I already use release/assets in another project) - but in this case I am not sure of the benefit because the script to build all package is already executed before release.