Add Editor#onTextInput hook, deprecate Editor#registerTextExpansion

[bantic]

Adds Editor#onTextInput, which accepts an object with the following properties:

• text — string; required if match is not present
• match — regex; required if text is not present
• run — callback

After a user types a character, the text preceding the cursor is compared to the input handlers. A handler is a match if the text prop is present and the preceding text ends with text, or if match is present and the preceding text matches match. The results of match.exec(userEnteredText) is passed to the handler's run.

This PR also deprecates Editor#registerTextExpansion because onTextInput covers the same use cases as text expansions and has a simpler API.

To add an @-mention handler one could do:

editor.onTextInput({
  text: '@',
  run(editor /*, matches=['@'] */) {
    let { range } = editor;
    let userName = window.prompt('Mention whom?');

    editor.selectRange(range.extend(-1)); // select the '@' character before the cursor
    editor.insertAtom('mention-atom', userName); // replaces the selected range with the atom
  }
});

cc @rlivsey

fixes #367

[bantic]

This can also be used to auto-format text. For example, this makes text with "*" on either side of it bold, like markdown, and auto-linkifies URLs:

editor.onTextInput({
  match: /(https?:\/\/[^ ]+) $/,
  run(editor, matches) {
    let url = matches[1];
    let range = editor.range;
    editor.selectRange(range.move(-1).extend(-1 * url.length)); // select the URL
    editor.run(postEditor => {
      let link = postEditor.builder.createMarkup('a', {href: url});
      postEditor.toggleMarkup(link);
    });

    editor.selectRange(range); // restore original cursor position
  }
});

editor.onTextInput({
  match: /\*([\w\s]+)\* $/,
  run(editor, matches) {
    let fullText = matches[0];
    let text = matches[1];
    let range = editor.range;

    editor.run(postEditor => {
      let strong = postEditor.builder.createMarkup('strong');
      let position = postEditor.deleteRange(range);

      position = postEditor.insertTextWithMarkup(position, text, [strong]);
      postEditor.insertTextWithMarkup(position, ' ', []); // restore non-bold space after the text
    });
  }
});

[bantic]

released in v0.9.5

[lessless]

👍