Enum members do not get their own page -- breaks links and search

[Levi-Lesches]

To reproduce:

• Go to https://pub.dev/documentation/flutter_local_notifications/18.0.1/flutter_local_notifications/DarwinNotificationActionOption.html
• Note that enum values do not have links in the main content section
• Note that the sidebar has links to these values. Clicking results in a 404
• Note that searching for any of the options, eg destructive, yields no results because there is no page to link to

[mkorbel1]

I think this also shows up if you reference an enum in a doc comment.

Something like

enum MyEnum {
  myVal,
}

/// Has something to do with [MyEnum.myVal].
void something() {}

[srawlins]

Sorry, this took me too long to address. Fix is in presubmit.