Merge pull request #32 from AlbertAZ1992/feat/support-for-ssr

feat: support ssr detecting

Author: Yanyan-Wang

packages/graph/src/workers/index.worker.ts

@@ -1,7 +1,7 @@
 import * as algorithm from './algorithm';
 import { MESSAGE } from './constant';
 
-const ctx: Worker = self as any;
+const ctx: Worker = (typeof self !== 'undefined') ? self : {} as any;
 
 interface Event {
   type: string;