Mark certain fields as "important"

[DanielRyanSmith]

After interacting with @nairnandu about requirements of feature data that are needed for items like the beta blog posts, it is obvious there are fields that are much more important than other fields when documenting a feature. Also, many users have noted that there are a very large number of fields in Chromestatus, and that it is difficult to know which fields are a high priority.

Although we don't have many "required" fields in the UI for good reason (required only later in the launch process, etc.), it may clear up ambiguity if we surface more important fields in an obvious way, and denote them as such.

Examples:

• Tracking bug URL
• Finch flag name or non-finch justification
• Intent to ship
• Milestone fields

[DanielRyanSmith]

Part of this work may be redundant with the work coming in #5495. Displaying that a field is in a specific intent is likely to signal to the user that a specific field is important already.