Add some bookmarks hg config to the bookmarks page

[kewisch]

There are a few things that will make working with bookmarks better:

• the hg evolve extension, despite it being experimental
• colors
• the hg wip command, which is defined through hgrc

I'd suggest we either link to or provide a .hgrc that includes some of the features Thunderbird developers commonly work with and make some recommendations on what extensions to enable.