function imapkey(keys, annotation, jscode, options) {
        _mapkey(insert, keys, annotation, jscode, options);
    }
Create a shortcut in insert mode to execute your own action.

@param {string} keys the key sequence for the shortcut.
@param {string} annotation a help message to describe the action, which will displayed in help opened by `?`.
@param {function} jscode a Javascript function to be bound. If the function needs an argument, next pressed key will be fed to the function.
@param {object} [options=null] `domain`: regex, a Javascript regex pattern to identify the domains that this mapping works, for example, `/github\.com/i` says that this mapping works only for github.com, `repeatIgnore`: boolean, whether this action can be repeated by dot command.

@see mapkey