0.3.2: bug fixes & QOL Improvements

There's a reasonable amount in this one but the main bugs that have been squashed are:

• #129 #223 #231 pop up windows and dialogues no longer make programs unresponsive(!)
• #244 manage_existing_clients now correctly avoids tiling windows that should be ignored
• #251 transient windows now render on the same workspace as their parent

New features:

• #265 @thebashpotato the DMenu helper now supports triggering dmenu-rs as well as the default suckless version
• #166 keybindings can now be updated while Penrose is running

This also includes an update of the dependency on x11rb to 0.11 from @psychon #250