Empty template strings freeze tokenizer

[kungfooman]

Because the while (txt.length) never decides on a regex (when no one matches) and just keeps trying all regexen again and again.

Example:

``

Fix: Add this regex to the literal string regex:

^\`\`

Another fix/idea: put tokens that weren't detected into their own "unknown" group while printing e.g. a warning to fix it later (instead of freezing).