monaco: minimal python support in gadget version

just set indentation rules for now XXX monaco does not set it
automatically ?

bt5/erp5_monaco_editor/SkinTemplateItem/portal_skins/erp5_monaco_editor/monaco-editor.gadget.js.js

@@ -144,6 +144,13 @@
             .push(addExtraLibrary('./monaco-renderjs.ts', 'renderjs'))
             .push(addExtraLibrary('./monaco-jio.ts', 'jio'));
         }
+        if (this.state.model_language === 'python') {
+          monaco.languages.setLanguageConfiguration('python', {
+            indentationRules: {
+              increaseIndentPattern: /^.*:$/
+            }
+          });
+        }
       }
       return queue;
     })