Using vimium to add custom javascript commands

With the ease of making site-specific key mappings, I would like to add in the ability for the user to execute arbitrary javascript one-liners on the open webpage with a vimium hook. This would allow savvy users to quickly enhance keyboard support for a unique site, and create new vimium commands.

For example, the following mapping and command would be possible:

map a javascript alert("Hello world!");

When the user presses 'a', vimium would eval the javascript stored under that command and alert the user.

I would be willing to code this feature, but I would like to ask a few things first:

1. This feature requires configuration, but would add a great amount of utility to vimium, greatly expanding its possible feature set. However, would it be applicable enough to be included in the master branch, or would it have to live on a fork.
2. I'm new to this project and coffeescript, though I have experience in javascript web development. Where would I get started adding this feature?
3. Would anyone else find this useful?

Thanks, all.
-Garrett

Start by reviewing Vimium’s custom key-mapping and command-handling paths, then examine how the project’s CoffeeScript and JavaScript are organized. Before implementation, resolve the configuration syntax and project-scope questions raised in the issue; done would require an agreed behavior for executing mapped JavaScript on the open webpage.