Use the light theme as the default one.

Signed-off-by: Akos Kitta <kittaakos@typefox.io>

arduino-ide-browser/package.json

@@ -26,5 +26,13 @@
         "prepare": "theia build --mode development",
         "start": "theia start --root-dir=../workspace",
         "watch": "theia build --watch --mode development"
+    },
+    "theia": {
+        "frontend": {
+            "config": {
+                "applicationName": "Arduino-PoC",
+                "defaultTheme": "light"
+            }
+        }
     }
 }