ButtonKeystroke is a mixin that provides a
keystroke prop that allows configuring
a function of the instance to be invoked upon the keystroke activation.
Lifecycle. Invoked once, both on the client and server, immediately before the initial rendering occurs.
Lifecycle. Invoked immediately before a component is unmounted from the DOM.
The keystroke definition. An object with the following properties:
- fn: The function to be executed
- keys: The keystroke definition, as expected by http://docs.ckeditor.com/#!/api/CKEDITOR.editor-method-setKeystroke
- name: The name for the CKEditor command that will be created. If empty, a random name will be created on the fly