Fix Jest test console errors

There is a known Jest bug documented here:
facebook/create-react-app#11928 regarding
an "experimental feature jsx" that is not supported. Apply the
workaround here, as well as set the Jest test environment to
"jsdom" for React Testing Library to properly run.

.babelrc

@@ -0,0 +1,5 @@
+{
+  "env": {
+    "test": { "presets": ["react-app"] }
+  }
+}

package.json

@@ -20,7 +20,9 @@
   "scripts": {
     "start": "react-scripts start",
     "build": "react-scripts build",
-    "test": "react-scripts test",
+    "test": "npm run test:types && npm run test:jest",
+    "test:jest": "jest",
+    "test:types": "tsc --noEmit",
     "eject": "react-scripts eject",
     "prepare": "husky install",
     "lint": "eslint src --ext .js,.ts,.tsx",
@@ -32,6 +34,9 @@
       "npm run lint"
     ]
   },
+  "jest": {
+    "testEnvironment": "jsdom"
+  },
   "eslintConfig": {
     "extends": [
       "react-app",