app.py: add a request counter

app.py

@@ -17,6 +17,7 @@ script_dir = os.path.dirname(os.path.abspath(__file__))
 
 def main():
     logging.basicConfig(level=logging.INFO)
+    counter = 0
 
     badges = """
     <div style="display: flex">
@@ -94,6 +95,8 @@ def main():
             if not src_ or not tgt_:
                 logging.warning("source or target are not provided")
                 return
+            logging.info(f"Making conversion request: [{counter}]")
+            counter += 1
             return vc_service_request(src_, tgt_)
 
         convert_btn.click(