add hall sensor uORB message

ASM3 · ASM3 · commit 2ffca74e4983 · 2021-04-14T16:18:54.000+02:00
diff --git a/msg/sensor_hall.msg b/msg/sensor_hall.msg
@@ -0,0 +1,7 @@
+uint64 timestamp			# time since system start (microseconds)
+
+int8 instance	            # sensor instance
+
+float32 mag_t	            # magnetic field measurement in Tesla
+
+float32 temp_c	            # temperature measurement in deg C
