Description:
    Creates a Default.sublime-keymap file.
    Default.sublime-keymap files contain a JSON array that contains JSON objects to specify the key bindings. The JSON objects must contain a keys and command key, and may also contain a args key if the command requires arguments.

Example:
    yo sublime-package:keymap

    This will create:
        keymaps/Default.sublime-keymap:                  *.sublime-keymap files contain a JSON array that contains JSON objects to specify the key bindings.

        keymaps/Default (Linux).sublime-keymap
        keymaps/Default (OSX).sublime-keymap
        keymaps/Default (Windows).sublime-keymap