Added mod tap with docs

kmk/handlers/modtap.py

@@ -0,0 +1,35 @@
+from kmk.kmktime import ticks_diff, ticks_ms
+
+
+def mt_pressed(key, state, *args, **kwargs):
+    # Sets the timer start and acts like a modifier otherwise
+    state.keys_pressed.add(key.meta.mod1)
+    if key.meta.mod2:
+        state.keys_pressed.add(key.meta.mod2)
+    if key.meta.mod3:
+        state.keys_pressed.add(key.meta.mod3)
+    if key.meta.mod4:
+        state.keys_pressed.add(key.meta.mod4)
+
+    state.start_time['mod_tap'] = ticks_ms()
+    return state
+
+
+def mt_released(key, state, *args, **kwargs):
+    # On keyup, check timer, and press key if needed.
+    state.keys_pressed.discard(key.meta.mod1)
+    if key.meta.mod2:
+        state.keys_pressed.discard(key.meta.mod2)
+    if key.meta.mod3:
+        state.keys_pressed.discard(key.meta.mod3)
+    if key.meta.mod4:
+        state.keys_pressed.discard(key.meta.mod4)
+    timer_name = 'mod_tap'
+    if state.start_time[timer_name] and (
+            ticks_diff(ticks_ms(), state.start_time[timer_name]) < state.config.tap_time
+    ):
+        state.hid_pending = True
+        state.tap_key(key.meta.kc)
+
+    state.start_time[timer_name] = None
+    return state