Replace Shields.io with locally rendered data/badges

[17cupsofcoffee]

Currently, data like download counts and licenses is displayed by embedding Shields.io badges as image tags. This PR (which is an extension of #589) replaces these entirely with data fetched directly from Crates.io/GitHub/GitLab.

There's two pretty big benefits to doing this:

• It makes the data more accessible to people who are using screen readers (we have no way of providing any meaningful alt text for the existing badges, as Shields.io doesn't provide any way of accessing the underlying data).
• It unlocks the possibillity of adding (client-side) sorting functionality later down the line.
  • This has been requested numerous times: resoruce sort #580, Sort crates by downloads #330

However, there are also some tradeoffs:

• The data will no longer be 100% up to date, as it'll only get fetched when the site re-renders.
  • This is done once a week, as well as when PRs are merged, though - so it should never get too stale.
• The site now takes a bit longer to build (1 minute on CI, as opposed to 30 seconds).
• Due to the extra requests to GitHub, we now have to provide a token to avoid getting rate-limited.
  • In fairness, this would have started happening as soon as we had more than 60 items with source = "github" anyway - the unauthenticated rate limit is very low!
  • GitHub Actions provides a token for every CI build anyway, but you'd have to provide one yourself if you're building locally.

I personally think these trade-offs are worth it (assuming I can get around to implementing the sorting functionality later!), but I'd be interested to get some feedback from the community on whether they think this is the right direction.

Here's what the new UI looks like (see the live page for comparison):

(the top three items there use the crates source, the last one uses the github source)

[ZimboPro]

What you could is keep the shields.io badges and just use the API calls to Github, Gitlab etc to power the alt data. This will allow that visually, it will be still up-to-date. The screen readers will be out of sync but just making a note somewhere on the page should help inform the users.

[17cupsofcoffee]

What you could is keep the shields.io badges and just use the API calls to Github, Gitlab etc to power the alt data. This will allow that visually, it will be still up-to-date. The screen readers will be out of sync but just making a note somewhere on the page should help inform the users.

That's what I was originally intending to do - I feel like that approach could make things confusing when I come to add the sorting functionality, though (as that would have to be driven by the local data). I'll give it some thought.