feat(f722): add usb mavlink transport

firmware/platforms/stm32f7/Cargo.toml

@@ -28,6 +28,7 @@ kaptan-mavlink = { path = "../../libs/kaptan-mavlink" }
 kaptan-sensor = { path = "../../libs/kaptan-sensor" }
 kaptan-spi = { path = "../../libs/kaptan-spi" }
 kaptan-time = { path = "../../libs/kaptan-time" }
+kaptan-tx = { path = "../../libs/kaptan-tx" }
 cortex-m = "0.7"
 cortex-m-rt = "0.7"
 rtic = { version = "2.3", default-features = false, features = [
@@ -37,4 +38,7 @@ stm32f7 = { version = "0.16", default-features = false, features = [
   "rt",
   "stm32f722",
 ] }
+synopsys-usb-otg = { version = "0.4", features = ["cortex-m", "fs"] }
+usb-device = "0.3"
+usbd-serial = "0.2"
 panic-halt = "1"