Focus, disable, enable, reset, and check emptiness

These methods are still exposed through the current context API. reset clears content and history, while isEmpty hides the internal empty paragraph that Summernote needs for focus handling.

Delete everything and then click Is empty? to see how Summernote reports emptiness.

State output
Ready.
Example configuration - Editor State
summernote.create('#editor-state-editor', {
  height: 260,
});

summernote.invoke('#editor-state-editor', 'focus');
summernote.invoke('#editor-state-editor', 'disable');
summernote.invoke('#editor-state-editor', 'enable');
const empty = summernote.invoke('#editor-state-editor', 'isEmpty');
summernote.invoke('#editor-state-editor', 'reset');