feat(main.py): Read the default application from the config file

preload/main.py

@@ -3,7 +3,13 @@ import os
 
 def main():
     # Try loading analog clock
-    default_app = "apps/analog_clock/__init__.py"
+    try:
+        import config
+
+        default_app = config.get_string("default_app")
+    except OSError:
+        default_app = "apps/analog_clock/__init__.py"
+
     try:
         with open(default_app, "r"):
             pass