code: function convertHTML(editor, node, pos) {
  	if (!containsPoint(node.open, pos)) {
  		return Promise.reject('Unsupported HTML context for data:URL convertion');
  	}
  
  	const srcAttr = getHTMLAttribute(node, 'src');
  	if (!srcAttr) {
  		return Promise.reject(`No "src" attribute in <${node.name}> tag`);
  	}
  
  	const src = srcAttr.value.value;
  	const replacementRange = getRange(srcAttr.value);
  	const m = src.match(reIsDataURL);
  
  	return m
  		? saveAsFile(editor, src.slice(m[0].length), replacementRange)
  		: convertToDataUrl(editor, src, replacementRange);
  }
docs: Converts to/from data:URL contents of `src` attribute of given HTML node
  @param  {TextEditor} editor
  @param  {Node}       node
  @param  {Point}      pos
  @return {Promise}