code: function getAttributeQuote(editor, attr) {
  	const range = new Range(attr.value ? attr.value.end : attr.end, attr.end);
  	return range.isEmpty() ? '' : editor.getTextInBufferRange(range);
  }
docs: Returns quote character, used for value of given attribute. May return empty
  string if attribute wasn’t quoted
  @param  {TextEditor} editor
  @param  {Object} attr
  @return {String}