Add a "Help URL" Field to the Page entity

It would be amazingly useful to be able to specify a "Help URL" for any Page, and for that to be displayed as a link/help button somewhere at the top of the page that would open that link in a new tab.

Frequently, the information entered into shotgun is expected to be formatted a certain way (see the 10-year-old feature request for field validation :/), or the page may play a part in some larger process that needs to be followed. 

As it is now, there is no easy way to get a user from the page in question to any documentation that may exist about it.