Which pretty much needs to be done together due to the amount of places
where they are compared together.
This also involves porting over StackOfOpenElements over to FlyString
from DeprecatedFly string to prevent a gazillion calls to
`.to_deprecated_fly_string` calls in HTMLParser.
This tokenizes a page's source to produce HTML with syntax highlighting.
The first implementation here is rather simple; we do not yet implement
code folding, line numbers, etc.
The goal is for this to be used as the View Source implementation for
all Ladybird chromes.