Handle raw GitHub URLs containing refs/heads/

[HebaruSan]

Problem

HideEmptyFilters currently has an inflation warning about failing to download a remote version file that most definitely exists.

Cause

Once upon a time, if you clicked the "raw" link in GitHub, it took you to a URL like this:

• https://raw.githubusercontent.com/HebaruSan/Astrogator/master/GameData/Astrogator/Astrogator.version

Now it does this instead:

• https://raw.githubusercontent.com/AlexSkylark/HideEmptyFilters/refs/heads/main/GameData/HideEmptyFilters/HideEmptyFilters.version

Note the extra refs/heads/ substring that's been added. GithubApi.TryGetGithubPath tries to parse GitHub URLs in order to access the same files via the GitHub API, and this new substring messes up the existing parsing. It thinks the branch is called refs and that the file's path starts with heads/main. When these erroneous strings are passed to the API, the retrieval fails.

Changes

Now GithubApi.TryGetGitHubPath skips refs/heads/ if it is present in a URL. This allows it to get the correct branch, and therefore also download the file successfully, which fixes the 404.

FYI to @AlexSkylark.