Expand libium's heuristic for github to use release name if only one jar is associated with the release

[garethgeorge]

Untested implementation that expands libium's heuristic for github releases to capture the common pattern of mod version in the release name with a single associated jar. For an example see Cow's odd widgets.

The heuristic implemented is:

• If there are multiple .jar assets, check for a version in the asset name.
• If there is a single .jar asset, check version in the asset name and fallback to the release name.

This code compiles, but I'm looking for guidance on testing pattern for libium as I'm not seeing tests in the repository and ran into some issues when trying to build ferium with a local copy.

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