Add support for source archives

[tranzystorekk]

Closes #52

Adding as draft to initiate discussion.

Important notes:

• switched the url used for normal assets to browser_download_url to make the common accepted content type application/vnd.github.raw work uniformly
• the progress bar displays just the downloaded bytes if the content length is unknown
• skipped implementing this feature for untag for now

[devmatteini]

Hi @tranzystorek-io! Thanks for the PR 🔝

I left some comments to check out :)

[devmatteini]

Hi @tranzystorek-io!
I was testing this changes a bit more and noticed that the progress bar was not rendering as soon as you selected an asset like it currently does.

I already pushed a fix for it :)

Apart from that, I think we can merge this PR

[devmatteini]

I still need to do some cleanup after the cross-platform release, but I think I will release a new version with these changes pretty soon :)

[tranzystorekk]

No probs, I wanted to have this officially packaged for Void Linux, but at least for now the maintainers don't see it add much value over gh 🫤