[Request] Check for Github releases for externals

[Gethe]

If an external links to a github repo, I think it would be useful to check if it has uploaded releases (like if they too use this packager) and optionally use that instead of the repo download.

[Nevcairiel]

Personally, I at least wouldn't want this to happen by default. My libraries are designed in such a way that packages are meant for people to download, and the repository is for the packager to pull from.

So if this is ever an option, it should be entirely optional.

[Gethe]

Oh of course, the default case shouldn't change.

[Tuller]

Maybe something like a warning message?

[ferronn-dev]

Maybe support URLs like the following:

https://github.com/ferronn-dev/lib-classic-gear-planner/releases/download/latest/LibClassicGearPlanner.zip

This doesn't even need to be a github-specific thing; just a "zip" or "archive" type. This would support github releases without having to explicitly support github releases.

[ferronn-dev]

Threw together https://github.com/BigWigsMods/packager/pull/105