feat(behaviors): Add &bootloader behavior.

* Allow reset behavior to have a type property.
* Add `bootloader` node that triggers DFU UF2
  bootloader mode using the AdaFruit nrf52
  bootloader.

app/dts/behaviors/reset.dtsi

@@ -1,3 +1,5 @@
+#include <dt-bindings/zmk/reset.h>
+
 / {
 	behaviors {
 		reset: behavior_reset {
@@ -5,5 +7,12 @@
 			label = "RESET";
 			#binding-cells = <0>;
 		};
+
+		bootloader: behavior_reset_dfu {
+			compatible = "zmk,behavior-reset";
+			label = "BOOTLOADER_RESET";
+			type = <RST_UF2>;
+			#binding-cells = <0>;
+		};
 	};
 };

app/dts/bindings/behaviors/zmk,behavior-reset.yaml

@@ -6,3 +6,8 @@ description: Keyboard Reset Behavior
 compatible: "zmk,behavior-reset"
 
 include: zero_param.yaml
+
+properties:
+  type:
+    type: int
+    default: 0