Support descriptions as hover text on projects

[seancorfield]

A PR will be coming for this.

The proposed solution:

• Support an optional description: field in the YAML file
• Render title="..." in the page containing this description

The PR will include the one-line descriptions that are currently on https://clojure-doc.org/articles/ecosystem/libraries_directory/ as a starting point, per our email discussion.

[seancorfield]

Closing this because it is implemented and live now. Thank you!