add packages for test

「babel-core: "7.0.0-bridge.0"」はこのエラーを回避するため

```
Requires Babel "^7.0.0-0", but was loaded with "6.26.3". If you are sure you have a compatible version of @babel/core, it is likely that something in your build process is loading the wrong version. Inspect the stack trace of this error to look for the first entry that doesn't mention "@babel/core" or "babel-core" to see what is calling Babel.
```

[reference]
FormidableLabs/spectacle#522 (comment)

package.json

@@ -8,7 +8,8 @@
   "scripts": {
     "build": "webpack --mode production --config webpack.config.js",
     "lint": "eslint --ext .js src",
-    "watch": "webpack --watch"
+    "watch": "webpack --watch",
+    "test": "jest"
   },
   "devDependencies": {
     "@babel/core": "^7.2.2",
@@ -19,12 +20,15 @@
     "@babel/plugin-syntax-import-meta": "^7.0.0",
     "@babel/plugin-transform-runtime": "^7.2.0",
     "@babel/preset-env": "^7.2.0",
+    "babel-jest": "23.4.0",
     "babel-loader": "^8.0.4",
     "babel-plugin-module-resolver": "^3.1.1",
     "copy-webpack-plugin": "^4.6.0",
     "css-loader": "^2.1.0",
     "eslint": "^5.11.0",
     "file-loader": "^3.0.1",
+    "jest": "^23.6.0",
+    "jest-jquery-matchers": "^2.1.0",
     "node-sass": "^4.11.0",
     "sass-loader": "^7.1.0",
     "style-loader": "^0.23.1",
@@ -34,6 +38,7 @@
   },
   "dependencies": {
     "@babel/runtime": "^7.2.0",
+    "babel-core": "7.0.0-bridge.0",
     "font-awesome": "^4.7.0",
     "jquery": "^3.3.1"
   }