add hold-tap interrupt behavior: prefer hold.

The interrupt resolution of hold-tap keys can now be set to resolve to
either tap or hold key. The default mod-tap is set to prefer hold.

kmk/key_validators.py

@@ -22,11 +22,11 @@ def layer_key_validator(layer, kc=None):
     return LayerKeyMeta(layer=layer, kc=kc)
 
 
-def mod_tap_validator(kc, mods=None):
+def mod_tap_validator(kc, mods=None, prefer_hold=True):
     '''
     Validates that mod tap keys are correctly used
     '''
-    return ModTapKeyMeta(kc=kc, mods=mods)
+    return ModTapKeyMeta(kc=kc, mods=mods, prefer_hold=prefer_hold)
 
 
 def tap_dance_key_validator(*codes):