[QUESTION] `RichTextEditor` update

Hi @artf , I'm thinking of opening a PR for an update on the RichTextEditor. I thought I'd run the idea past you first before getting to work on it. It proposes a change to the actions to have a state, which is an optional function that returns an integer to depict the state of each action; 1 for active, 0 for inactive, -1 for disabled. This essentially allows the ability to set the styling and functionality of the actions without having to set the name field of the object the same as the Document.queryCommandSupported or Document.queryCommandState parameter. If there is no state function provided, we can default to the previous logic An example use case for this the inserting and removing of an anchor:

editor.RichTextEditor.add('insertAnchor', {
  icon: '<i class="fa fa-link"/>',
  attributes: {title: 'Insert link'},
  state: (doc, rte) => {
    const anchor = rte.selection().anchorNode;
    const nextSibling = anchor && anchor.nextSibling;
    if (nextSibling && nextSibling.nodeName == 'A') {
      // If we've selected an anchor tag, return positive
        return 1;
    } else {
      // since you can nest anchor tags, we technically don't want to `disable` this command
      // so we return 0 for inactive.
      return 0;
    }
  },
  result: rte => rte.insertHTML(`<a class="link" href="">${rte.selection()}</a>`)
});

editor.RichTextEditor.add('removeAnchor', {
  icon: '<i class="fa fa-unlink"/>',
  attributes: {title: 'Remove link'},
  state: (doc, rte) => {
    const anchor = rte.selection().anchorNode;
    const nextSibling = anchor && anchor.nextSibling;
    if (nextSibling && nextSibling.nodeName == 'A') {
      // If we've selected an anchor tag, return 0 for inactive, meaning we can toggle this command.
        return 0;
    } else {
      // however, if they have not selected an anchor tag, this action should be `disabled`
      return -1;
    }
  },
  result: rte => rte.exec('unlink')
});

Also, what do you think about the idea of passing an empty array to actions on the config, not rendering any of the default actions. I say this because, I'm creating my own RTE without using CKEditor (as CKEditor has some unusual behaviour with custom components), and in order to not render the bold action first, I pass it in the actions: ['bold'] configuration, but then editor.RichTextEditor.remove('bold'), as I would like have other commands before the bold and this is the only way i could think of doing so

I'm very happy to work on this, just thought I'd get your input/concerns/blessing first