fix: support esm define when running under virtual kernel

When we define a esm top level in a module, we don't need to create
the module widget. However, if we do this during the running of the
app under the context of a virtual kernel, we should directly
create the esm widget.

Should fix the failing of widgetti/ipyantd#4

solara/server/esm.py

@@ -28,6 +28,8 @@ def define_module(name, module: Union[str, Path]):
     if name in _modules:
         old_module, dependencies = _modules[name]
     _modules[name] = (module, dependencies)
+    if kernel_context.has_current_context():
+        create_modules()
     return None