Add tag descriptions into the Hub

[tbarn]

Feature request

Use the tag descriptions from the OAS file in documentation Hubs

For example: If the tags are being used for groups and a user might want to add an introduction to that grouping through the tag description

[jayshao]

I often use tags to group operations on entities (because I'm neurotic about doing batch operations on aggregate roots, and individual operations with a {id} path param) and think this would make the docs much cleaner/more readable. It would be really nice to have an "entity-level description"

Ideally with some kind of reference/macro to include the description directly from a Model... :)