refactor(editor): move extension to store (#9552)

blocksuite/framework/store/src/extension/index.ts

@@ -0,0 +1,17 @@
+import type { Container } from '@blocksuite/global/di';
+
+/**
+ * Generic extension.
+ * Extensions are used to set up the dependency injection container.
+ * In most cases, you won't need to use this class directly.
+ * We provide helper classes like `CommandExtension` and `BlockViewExtension` to make it easier to create extensions.
+ */
+export abstract class Extension {
+  static setup(_di: Container): void {
+    // do nothing
+  }
+}
+
+export interface ExtensionType {
+  setup(di: Container): void;
+}