Automatically publish latest snapshot build on Release page

[rgrunber]

We can publish our latest snapshot on the releases page under some tag like latest, and as a pre-release, using https://github.com/marvinpinto/action-automatic-releases .

Thanks to @fbricon for investigating this.

[rgrunber]

Slight problem. This would transition our builds to publish vsix snapshots on GH actions and releases would likely remain under Jenkins (for now?). The problem is that every build of a vscode-xml vsix embeds a LemMinX language server. That same language server needs to be built and hosted somewhere as a binary, otherwise our snapshot builds will not support the binary case out-of-the-box.

So a requirement for this is to host the LemMinX binaries as a GitHub release also. I'm guessing this can be hosted on the LemMinX vscode-xml side and there is a GHA script for this. We can just update our binaryServerDownloadUrl as part of the the snapshot builds.

The pain point here is we're porting the builds to GHA for snapshots, which isn't as trivial (due to the binaries), and we still have to maintain the Jenkinsfiles.

[rgrunber]

With eclipse-lemminx/lemminx#1184, we'll have snapshots published to a URL like https://github.com/eclipse/lemminx/releases/download/latest/lemminx-${platform} . We can then use that as the binaryServerDownloadUrl, and then we just need to publish release snapshots for the vsix here.