fix(deps): upgrade dom-testing-library (#14)

* Add missing jest config setting

See https://stackoverflow.com/a/51554619/621809

* Upgrade dom-testing-library

Also upgraded `serve` because it was giving a warning when running it.

Author: gnapse

jest.config.js

@@ -2,4 +2,5 @@ const jestConfig = require('kcd-scripts/jest')
 
 module.exports = Object.assign(jestConfig, {
   testEnvironment: 'jest-environment-jsdom',
+  testURL: 'http://localhost/',
 })

package.json

@@ -39,13 +39,13 @@
   "author": "Kent C. Dodds <kent@doddsfamily.us> (http://kentcdodds.com/)",
   "license": "MIT",
   "dependencies": {
-    "dom-testing-library": "^2.0.0"
+    "dom-testing-library": "^3.4.0"
   },
   "devDependencies": {
     "cypress": "^3.0.1",
     "kcd-scripts": "^0.37.0",
     "npm-run-all": "^4.1.2",
-    "serve": "^7.2.0",
+    "serve": "^10.0.0",
     "wait-port": "^0.2.2"
   },
   "peerDependencies": {