Fix markdown formatting in README.md

Author: MrXANA91

README.md

@@ -1,16 +1,16 @@
-## Arduino
+# Arduino
 All my arduino projects
 
-# ESP32_TEMPERATURE
+## ESP32_TEMPERATURE
 ESP32 connects to a MQTT server via WiFi and put temperature and humidity values into topics
 
-# libraries
+## libraries
 - HC-SR04 functions
 - MQ7 functions
 - MS5803_02BA functions
 
-# test_HR-SR04
+## test_HR-SR04
 HR-SR04 ultrasound modules test
 
-# test_MQ7
+## test_MQ7
 MQ7 carbon monoxyde modules test