Update default rule doc title format and show description notice by default

[nzakas]

Right now, the main title on each rule page is the old ESLint format of "description (rule-id)", which can be quite long.

The ESLint docs switched to having the rule-id as the primary heading with the description underneath it, so I'd like to see this change here as well.

[bmish]

One note is that we do have an option --rule-doc-title-format to control the title format. I would be open to changing the default to prefix-name in a future major version, since I agree that would make the title simpler and more concise.

As for the description, we need to implement a NOTICE_TYPE to include the description under the title. This would enable us to ensure we still include the description even after a change to the default title format. Done in: #350.