Add CI

firmware/main_mcu/platformio.ini

@@ -16,6 +16,17 @@ lib_deps =
 	knolleary/PubSubClient@^2.8.0
 	bblanchon/ArduinoJson@^6.17.2
 upload_speed = 115200
+src_filter =
+    ;; Default filter
+    +<*>
+    -<.git/>
+    -<.svn/>
+    -<example/>
+    -<examples/>
+    -<test/>
+    -<tests/>
+	;; Don't compile until the user adds their own config
+	-<src/config-example.h>
 
 [env:button-release]