Adds mousetrap-global-bind definitions and updates mousetrap to be loadable as an external module

This PR has two changes:

* First, I added type definitions for Mousetrap's global-bind plugin.
* Second, I extended Mousetrap's type definition to allow Mousetrap to be loaded as an external module: "mousetrap"

In both cases I've added the required tests.

If you'd like me to split these into two PRs, I can do that.