feat: human-readable display for back matter media types

[kylelaker]

This updates how we display resources in Back Matter to try to use a more human-readable name. When media-type is provided, we prefer that; otherwise we fallback to guessing based on the file extension using the mime-db package's database (which includes registrations with IANA as well as the Nginx and Apache databases).

The media types are largely those defined in #111 though with some additional ones found during the implementation that may be useful. The lookup algorithm is not significantly modified besides the feedback given in the issue comments.

The UI is also updated slightly to give more visual indication that it's a button and can be clicked to open the link.

Closes: #111

Screenshots

General Display:

OSCAL Media Types:

[kylelaker]

Todo:

• Better document how the lookups are performed
• Write tests for the new code

[tuckerzp]

This is looking really good so far. After seeing your implementation, I now agree mime-db is the better choice here.

[Bronstrom]

This is looking good so far @kylelaker! I'm liking the choices you've made with capturing and formatting the media types are great and I think "Unrecognized" is a good fallback for when the media type isn't found.

[Bronstrom]

Thanks for your work on this @kylelaker! I appreciate the documentation providing more reasoning on the less clear parts of the code.