Add yaw modes that define multirotor heading behaviour during missions.

src/modules/navigator/mission_params.c

@@ -95,3 +95,19 @@ PARAM_DEFINE_FLOAT(MIS_DIST_1WP, 500);
  * @group Mission
  */
 PARAM_DEFINE_INT32(MIS_ALTMODE, 0);
+
+/**
+ * Multirotor only. Yaw setpoint mode.
+ *
+ * 0: Set the yaw heading to the yaw value specified for the destination waypoint.
+ * 1: Maintain a yaw heading pointing towards the next waypoint.
+ * 2: Maintain a yaw heading that always points to the home location.
+ * 3: Maintain a yaw heading that always points away from the home location (ie: back always faces home).
+ *
+ * The values are defined in the enum mission_altitude_mode
+ *
+ * @min 0
+ * @max 3
+ * @group Mission
+ */
+PARAM_DEFINE_INT32(MIS_YAWMODE, 0);