main/gtk+3.0: add patch to fix touch on slow devices

We've run this on laptops in postmarketOS for a very long while, without remarkable issues. This greatly helps in performance with slow devices (e.g: SoCs and phones), and wont get accepted upstream due to it being in feature freeze, and requiring more extensive changes to input to not be "just a hack". This seems, however, a sensible patch downstream for an old version of the project

CC: @Newbyte