Add @document menus to Insert menu

[yfdyh000]

I hope that users can easily understand and access these matching.

https://developer.mozilla.org/en-US/docs/Web/CSS/@document
https://github.com/JasonBarnabe/stylish/wiki/Valid-@-moz-document-rules

Due to a Mozilla quirk, I can not gracefully handle the accesskeys for like "For Domain" or "_@_document url", so I use the "rule" of crappy as menu labels.

We can put them in a sub-menu, but it looks is not necessary, we have plenty of space, and save a operation.

[JasonBarnabe]

I don't think this is very useful. To be useful, I would say:

1. It should prompt the user for what they want to do, at least asking if they want that specific URL, URLs starting with that, all URLs on that domain. For extra fanciness you could let them generate and test a regexp.
2. It should insert it at the caret position, and if there's a selection, it should surround it with the block. Bonus points for ensuring that it's in a valid spot.
3. Even more bonus points: being able to edit an existing -moz-document.

[yfdyh000]

It is an code with individual view, I never able to remember them.

1. a prompt? This may increase the complexity while user input. For a regex tester, I feel it should not be repeated achieve in the internal.
2. A hacking tip, but I guess it might scare the user's knowledge. This is a simple insert, I don't want it to become an intelligent tool, although it is possible.
3. Sounds good, but what is more? a default values? menu order? show/hide?