In order to actually view the web as it is, we're gonna need a proper
HTML parser. So let's build one!
This patch introduces the Web::HTMLTokenizer class, which currently
operates on a StringView input stream where it fetches (ASCII only atm)
codepoints and tokenizes acccording to the HTML spec tokenization algo.
The tokenizer state machine looks a bit weird but is written in a way
that tries to mimic the spec as closely as possible, in order to make
development easier and bugs less likely.
This initial version is far from finished, but it can parse a trivial
document with a DOCTYPE and open/close tags. :^)
