feat(behaviors): Add behavior metadata information.

* For upcoming ZMK studio work, make a set of rich metadata available
  to provide a friendly name for a behavior, and allow super flexible
  descriptions of the parameters the behaviors take.
* Add ability to validate a zmk_behavior_binding against
  the behavior metadata available.

app/dts/behaviors/mod_tap.dtsi

@@ -12,6 +12,7 @@
             flavor = "hold-preferred";
             tapping-term-ms = <200>;
             bindings = <&kp>, <&kp>;
+            display-name = "Mod-Tap";
         };
     };
 };