Combine usage stats across package platforms

Inspired by a Mastodon thread with @woodruffw, @ianlewis and @joshbressers: https://mastodon.social/@andrewnez/114870983231431338

Would be great to track and graph package usage across multiple platforms – e.g. PyPI, Conda, Homebrew, npm, etc – in one place. Right now the data is split across tools like pepy.tech, Conda stats, etc, and there’s no easy way to see overall trends for a project like zizmor which is published on many package managers.

- Pull in download/usage stats from different sources
- Match package names/identities across ecosystems (by repository_url is currently the easiest way to do it)
- Show a combined charts and breakdowns by ecosystem
- if stats are available at a per version level then do that too.