[hdpowerview] Add new signal strength channel (#11198)

* Add new signal strength channel.

Fixes #11197

Signed-off-by: Jacob Laursen <jacob-github@vindvejr.dk>

bundles/org.openhab.binding.hdpowerview/src/test/java/org/openhab/binding/hdpowerview/HDPowerViewJUnitTests.java

@@ -355,6 +355,8 @@ public class HDPowerViewJUnitTests {
 
             pos = shadePos.getState(PRIMARY_ACTUATOR, VANE_COORDS);
             assertEquals(UnDefType.class, pos.getClass());
+
+            assertEquals(4, shadeData.signalStrength);
         } catch (JsonParseException e) {
             fail(e.getMessage());
         }