Remove unused files in the PlatformIO package

library.json

@@ -12,11 +12,9 @@
     "name": "Benoit Blanchon",
     "url": "https://blog.benoitblanchon.fr"
   },
-  "exclude": [
-    ".devcontainer",
-    ".github",
-    "extras"
-  ],
+  "export": {
+    "include": ["src", "examples", "LICENSE.txt", "ArduinoJson.h"]
+  },
   "frameworks": "*",
   "platforms": "*",
   "build": {