Support recommended description lengths on pub.dev home page

We dock points from packages that have a description that is outside 60 < n < 180 characters.

But our homepage tiles are optimized for descriptions that are < 60 characters:

The result is that the tiles often maddeningly omit the keywords that describe the package function:

We need to do a better job in managing longer titles. A couple of ideas:

- Add an ellipsis with a tooltip, so you can hover over and see more information
- Adjust the text size or tile dimensions so that it can show the recommended text length

I'm also open to a different solution outside of pub.dev (e.g. introducing a `short_description` field in YAML that we use for these settings, or changing the recommended description length to match the pub.dev tile size).