Update guess_is_regexp.js

[jkomyno]

Fixes failure case. For instance, consider the following:

import { AppRegistry } from 'react-native';
// import './ReactotronConfig';
import { App } from 'app/root';
AppRegistry.registerComponent('MyApp', () => App);

With the previous version of REGEXP_PRECEDER_TOKEN_RE, it would have failed to find out that L#2 is a comment. Now it has this capability.

[mikesamuel]

It seems like there might be a separate bug. Where is guess_is_regexp being called for a //... token?

11.8.5 Regular Expression Literals says

NOTE 2 Regular expression literals may not be empty; instead of representing an empty regular expression literal, the code unit sequence // starts a single-line comment. To specify an empty regular expression, use: /(?:)/.

Though not explicitly called out, an analysis of the grammar shows that /* cannot start a regexp literal since * is a suffix operator and its operand does not match the empty string.