docs(custom_js): add more comment to code example

examples/09_advanced/custom_js/app.py

@@ -10,26 +10,33 @@ def load_my_js(server):
     js_file = Path(__file__).with_name("my_utils.js").resolve()
     server.enable_module(
         dict(
-            serve={"my_code": str(js_file.parent)}, scripts=[f"my_code/{js_file.name}"]
+            # Path to serve under /my_code
+            serve={"my_code": str(js_file.parent)},
+            # JS file(s) to load
+            scripts=[f"my_code/{js_file.name}"],
         )
     )
 
 
 class CustomAddOnJS:
     def __init__(self, server=None, table_size=10):
         self.server = get_server(server, client_type="vue3")
-        load_my_js(self.server)
         self.ui = self._build_ui()
 
+        # Make sure my js code get loaded on the client side
+        load_my_js(self.server)
+
     def _build_ui(self):
         with SinglePageLayout(self.server, full_height=True) as layout:
             with layout.content:
                 vuetify3.VTextField(
                     v_model=("text_1", "1.2"),
+                    # Use our extended trame.utils in template definition
                     rules=("[utils.my_code.rules.number]",),
                 )
                 vuetify3.VTextField(
                     v_model=("text_2", "2"),
+                    # Use our extended trame.utils in template definition
                     rules=("[utils.my_code.rules.int]",),
                 )
 

examples/09_advanced/custom_js/my_utils.js

@@ -1,3 +1,5 @@
+// global trame.utils can be extended by users
+// - within template definition, it can be accessed as "utils.my_code.rules.int"
 window.trame.utils.my_code = {
     rules: {
         number(v) {