Poor performance on html files

[jpramosi]

Hello, at first I would like to thank you for the project!
I've found an issue with the html rewriter: The problem is a new regex is compiled every time lol-html its rewriter handler is called here.
Moving the regex instance to a static variable like here improves the rewriting time for an average html file from ~2 seconds to 50-200 milliseconds on some pages.
The result is that the initial page loads much faster with no noticeable delay.