An upcoming commit will migrate the contents of Headers.h/cpp to LibHTTP
for use outside of LibWeb. These CORS and MIME helpers depend on other
LibWeb facilities, however, so they cannot be moved.
When detecting an element's opening tag, the spec asks us to skip ahead
to the first whitespace or end chevron character before trying to read
attributes. Instead, we were always skipping 2 positions ahead and then
ignoring all whitespace characters and slashes, which was clearly wrong.
Theoretically this could have caused some weird behaviors if part of the
opening tag matched an expected attribute name, but it's very unlikely
to see that in the wild.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
