Previously, we could connect to our DevTools server from Firefox, but
could not see any information on Ladybird's opened tabs. This implements
enough of the protocol to see a tab list, but we cannot yet inspect the
tabs.
To aid with debugging web page issues in Ladybird without needing to
implement a fully fledged inspector, we can implement the Firefox
DevTools protocol and use their DevTools. The protocol is described
here:
https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html
This commit contains just enough to connect to Ladybird from a DevTools
client.