Initial USB HID implementation

- One button reported as gamepad button
- One LED controlable via application specific HID report and FlyWithLua

CMakeLists.txt

@@ -0,0 +1,23 @@
+cmake_minimum_required(VERSION 3.13)
+
+# initialize pico-sdk from submodule
+# note: this must happen before project()
+include(pico-sdk/pico_sdk_init.cmake)
+
+project(rp2040_hid)
+
+# initialize the Raspberry Pi Pico SDK
+pico_sdk_init()
+
+add_executable(rp2040_hid
+  src/main.c
+  src/usb_config.c
+)
+
+# Add pico_stdlib library which aggregates commonly used features
+target_link_libraries(rp2040_hid pico_stdlib pico_unique_id tinyusb_device tinyusb_board)
+target_include_directories(rp2040_hid PRIVATE src)
+
+
+# create map/bin/hex/uf2 file in addition to ELF.
+pico_add_extra_outputs(rp2040_hid)