Add README

README.txt

+Raspberry Pi Program for the SOTSEF LED Reactions Game
+
+Dependencies:
+
+- Gtk 4 (sudo apt install libgtk-4-dev)
+- librsvg (sudo apt install librsvg2-dev)
+- blueprint-compiler (Get it from
+  https://gitlab.gnome.org/jwestman/blueprint-compiler/-/releases/v0.14.0,
+  the debian repo version is really out of date)
+- WiringPi (https://github.com/WiringPi/WiringPi; it's not in the debian
+  repo)
+
+Building:
+
+```
+./configure build
+ninja -C build
+```
+
+Running:
+
+```
+./build/game
+```