setKeepAlive function added issue #153 (#170)

Co-authored-by: Allen Benter <allen.benter@dpi.nsw.gov.au>

src/HAMqtt.cpp

@@ -183,6 +183,11 @@ bool HAMqtt::isConnected() const
     return _mqtt->connected();
 }
 
+void HAMqtt::setKeepAlive(uint16_t keepAlive)
+{
+    _mqtt->setKeepAlive(keepAlive);
+}
+
 void HAMqtt::addDeviceType(HABaseDeviceType* deviceType)
 {
     if (_devicesTypesNb + 1 > _maxDevicesTypesNb) {

src/HAMqtt.h

@@ -203,6 +203,11 @@ public:
      */
     bool isConnected() const;
     
+    /**
+     * sets keepAlive value.
+     */
+    void setKeepAlive(uint16_t keepAlive);
+
     /**
      * Adds a new device's type to the MQTT.
      * Each time the connection with MQTT broker is acquired, the HAMqtt class