added e2e tests (#298)

- added e2e tests for
  - banner
  - history
  - intro
  - language
  - link
- added e2e workflow
- added cypress badge to README

cypress/webpack.config.js

@@ -0,0 +1,22 @@
+const path = require('path')
+
+module.exports = {
+  entry: './src/index.ts',
+  module: {
+    rules: [
+      {
+        test: /\.tsx?$/,
+        use: 'ts-loader',
+        exclude: /node_modules/
+      }
+    ]
+  },
+  resolve: {
+    extensions: ['.tsx', '.ts', '.js']
+  },
+  output: {
+    filename: 'bundle.js',
+    path: path.resolve(__dirname, 'dist')
+  }
+}
+