added an rc switch for arming and disarming with the option to use it as a button

src/modules/sensors/sensor_params.c

@@ -2488,6 +2488,34 @@ PARAM_DEFINE_INT32(RC_MAP_OFFB_SW, 0);
  */
 PARAM_DEFINE_INT32(RC_MAP_KILL_SW, 0);
 
+/**
+ * Arm switch channel
+ *
+ * @min 0
+ * @max 18
+ * @group Radio Switches
+ * @value 0 Unassigned
+ * @value 1 Channel 1
+ * @value 2 Channel 2
+ * @value 3 Channel 3
+ * @value 4 Channel 4
+ * @value 5 Channel 5
+ * @value 6 Channel 6
+ * @value 7 Channel 7
+ * @value 8 Channel 8
+ * @value 9 Channel 9
+ * @value 10 Channel 10
+ * @value 11 Channel 11
+ * @value 12 Channel 12
+ * @value 13 Channel 13
+ * @value 14 Channel 14
+ * @value 15 Channel 15
+ * @value 16 Channel 16
+ * @value 17 Channel 17
+ * @value 18 Channel 18
+ */
+PARAM_DEFINE_INT32(RC_MAP_ARM_SW, 0);
+
 /**
  * Flaps channel
  *
@@ -2985,6 +3013,24 @@ PARAM_DEFINE_FLOAT(RC_OFFB_TH, 0.5f);
  */
 PARAM_DEFINE_FLOAT(RC_KILLSWITCH_TH, 0.25f);
 
+/**
+ * Threshold for the arm switch
+ *
+ * 0-1 indicate where in the full channel range the threshold sits
+ * 		0 : min
+ * 		1 : max
+ * sign indicates polarity of comparison
+ * 		positive : true when channel>th
+ * 		negative : true when channel<th
+ *
+ * @min -1
+ * @max 1
+ * @group Radio Switches
+ *
+ *
+ */
+PARAM_DEFINE_FLOAT(RC_ARMSWITCH_TH, 0.25f);
+
 /**
  * Threshold for the VTOL transition switch
  *