feat(mouse): Initial mouse keys support.

* Add HID report/descriptor for a new report with mouse buttons,
  and x/y/wheel deltas.
* New mouse key press behavior for press/release of mouse keys.
* Add constants for HID main item values (e.g. data/array/absolute)
* Define and use constants for our HID report IDs.

app/Kconfig

@@ -156,6 +156,10 @@ config ZMK_BLE_CONSUMER_REPORT_QUEUE_SIZE
     int "Max number of consumer HID reports to queue for sending over BLE"
     default 5
 
+config ZMK_BLE_MOUSE_REPORT_QUEUE_SIZE
+    int "Max number of mouse HID reports to queue for sending over BLE"
+    default 20
+
 config ZMK_BLE_CLEAR_BONDS_ON_START
     bool "Configuration that clears all bond information from the keyboard on startup."
     default n
@@ -315,6 +319,15 @@ endif
 #Display/LED Options
 endmenu
 
+menu "Mouse Options"
+
+config ZMK_MOUSE
+    bool "Enable ZMK mouse emulation"
+    default n
+
+#Mouse Options
+endmenu
+
 menu "Power Management"
 
 config ZMK_BATTERY_REPORTING