add support of unitMeasure for Numbers

src/ha.h

@@ -245,6 +245,7 @@ namespace Ha {
         unsigned int min = 1;
         unsigned int max = 100;
         unsigned int step = 1;
+        const char* unitMeasure = nullptr;
 
         Number(const char* name, const char* id, onMessage f) : Component(id, name, "number"), StatefulCommand(this, f) {}
 
@@ -258,6 +259,7 @@ namespace Ha {
             jsonDoc["min"] = min;
             jsonDoc["max"] = max;
             jsonDoc["step"] = step;
+            if (unitMeasure) jsonDoc["unit_of_measurement"] = unitMeasure;
         }
     };