* Change register account dialog to show instructions
Change data forms to handle title and instructions elements
* Change register account dialog to show fixed fields
Closes #988
* Change form switch to halign start
Closes #992
* Change register account dialog to markup URLs
On non-toplevel windows, use Container.remove() instead of Widget.destroy()
Needed for migration to GTK4
https://developer.gnome.org/gtk4/unstable/gtk-migrating-3-to-4.html#id-1.7.4.3.17