Allow adding buttons to Action header

[AshotN]

Describe the problem feature solves
Right now the only way to add a button to the header of a resource/record is to use a custom action. I want to create a button that is simply a link to a different page.

Describe the solution you'd like
The ability to pass a custom component to the header

Describe alternatives you've considered
Creating an action with a custom component that just acts as a redirect

Acceptance criteria

• Pass component to header
• Document this feature

[dziraf]

Potential implementation:

• add href option to Action config
• handler should be optional
• if href is specified but handler isn't, the UI button should simply open the link