New esp8266_4MB_max entry to test usermods / i2c

pio.ini: add esp8266_4MB_max with pir, dallas, relay  games (to test IMU) 

addHB: use string literal instead of var

appendConfigData to um multirelay

usermods/multi_relay/usermod_multi_relay.h

@@ -571,6 +571,11 @@ class MultiRelay : public Usermod {
       DEBUG_PRINTLN(F("MultiRelay config saved."));
     }
 
+    void appendConfigData()
+    {
+      oappend(SET_F("addHB('MultiRelay');"));
+    }
+
     /**
      * restore the changeable values
      * readFromConfig() is called before setup() to populate properties from values stored in cfg.json