feat: Add E2E tests (#4)

package.json

@@ -4,7 +4,8 @@
   "main": "index.js",
   "license": "MIT",
   "scripts": {
-    "build": "webpack"
+    "build": "webpack",
+    "test": "jest"
   },
   "devDependencies": {
     "@ant-design/icons": "^4.2.2",
@@ -13,7 +14,11 @@
     "@babel/preset-react": "^7.10.4",
     "@babel/preset-typescript": "^7.10.4",
     "@hot-loader/react-dom": "^16.13.0",
+    "@types/express": "^4.17.11",
+    "@types/fs-extra": "^9.0.7",
+    "@types/get-port": "^4.2.0",
     "@types/html-webpack-plugin": "^3.2.3",
+    "@types/jest": "^26.0.20",
     "@types/jszip": "^3.4.1",
     "@types/openpgp": "^4.4.12",
     "@types/react": "^16.9.46",
@@ -29,11 +34,17 @@
     "babel-plugin-transform-inline-environment-variables": "^0.4.3",
     "css-loader": "^4.2.1",
     "dotenv": "^8.2.0",
+    "express": "^4.17.1",
+    "fs-extra": "^9.1.0",
+    "get-port": "^5.1.1",
     "html-webpack-plugin": "^4.3.0",
+    "jest": "^26.6.3",
     "offline-plugin": "^5.0.7",
     "parcel-bundler": "^1.12.4",
+    "puppeteer": "^7.1.0",
     "react-hot-loader": "^4.12.21",
     "style-loader": "^1.2.1",
+    "ts-jest": "^26.5.1",
     "ts-node": "^8.10.2",
     "typescript": "^3.9.7",
     "webpack": "^4.44.1",