feat: better support shadow dom queries (#45)

Upgrade @testing-library/dom to better support shadow dom queries

@testing-library/dom v7 has an issue querying for elements with
aria-labels contained in a shadow dom.

Author: segovia

package.json

@@ -32,7 +32,7 @@
   "license": "ISC",
   "dependencies": {
     "@babel/runtime": "^7.4.3",
-    "@testing-library/dom": "^7.0.4",
+    "@testing-library/dom": "^8.17.1",
     "simmerjs": "^0.5.6"
   },
   "peerDependencies": {