Add old river init script

This is so I remember how to initialize river if I want to use it again,
although I currently have no plans to do so.

river.sh

@@ -0,0 +1,7 @@
+export BROWSER="librewolf"
+export GTK_IM_MODULE=fcitx
+export QT_IM_MODULE=fcitx
+export XMODIFIERS=@im=fcitx
+export GLFW_IM_MODULE=ibus
+
+exec river