[Add] intersection observer test용 모듈 추가 #32

why
테스트환경은 브라우저이기 때문에 intersection api 가 없음

how
mock 모듈 추가로 테스트 통과하게 설정

client/package.json

@@ -12,7 +12,9 @@
     "eslint": "^6.6.0",
     "eslint-config-airbnb-base": "^14.0.0",
     "eslint-plugin-import": "^2.18.2",
-    "prettier": "^1.19.1"
+    "intersection-observer": "^0.7.0",
+    "prettier": "^1.19.1",
+    "react-intersection-observer": "^8.25.1"
   },
   "dependencies": {
     "@apollo/react-components": "^3.1.3",

client/src/App.test.tsx

@@ -3,6 +3,8 @@ import ReactDOM from 'react-dom';
 import App from './App';
 import { ApolloProvider } from '@apollo/react-hooks';
 import client from './apollo/ApolloClient';
+import 'intersection-observer';
+import 'react-intersection-observer';
 
 it('renders without crashing', () => {
   const div = document.createElement('div');