DEV: patchbot: support passing the page settings in the URL fragment

DEV: patchbot: support passing the page settings in the URL fragment

It's difficult to point a coworker to a set of patches resulting from a
selection. Some browser-based tools such as slides pass information in
the URL as a fragment that the code in the browser is able to retrieve.
Conversely it's possible to update it without causing a page reload
using history.replaceState(). This means that we can instantly update
the URL bar with extra params passed as fragments as we click on the
page, so it's possible to copy-paste a current state so that someone
else gets the same view (without local edits).