Add debug hooks to the event dispatcher, remove explicit prints

kmk/common/event_defs.py

@@ -0,0 +1,18 @@
+from micropython import const
+
+KEY_UP_EVENT = const(1)
+KEY_DOWN_EVENT = const(2)
+
+
+def key_up_event(keycode):
+    return {
+        'type': KEY_UP_EVENT,
+        'keycode': keycode,
+    }
+
+
+def key_down_event(keycode):
+    return {
+        'type': KEY_DOWN_EVENT,
+        'keycode': keycode,
+    }