/**
* Parses an HTML string, calling the callbacks to notify of tags and text.
*
* ## History
*
* This file previously used a regular expression to find html tags in the input
* text. Unfortunately, we ran into a bunch of catastrophic backtracking issues
* with certain input text, causing Autolinker to either hang or just take a
* really long time to parse the string.
*
* The current code is intended to be a O(n) algorithm that walks through
* the string in one pass, and tries to be as cheap as possible. We don't need
* to implement the full HTML spec, but rather simply determine where the string
* looks like an HTML tag, and where it looks like text (so that we can autolink
* that).
*
* This state machine parser is intended just to be a simple but performant
* parser of HTML for the subset of requirements we have. We simply need to:
*
* 1. Determine where HTML tags are
* 2. Determine the tag name (Autolinker specifically only cares about ,
*