Chore: Fixes PhantomJs by adding polyfills for fetch and AbortController (#21655)

* Chore: Fixes PhantomJs rendering

* Docs: Updated docs

* Update contribute/style-guides/e2e.md

Co-Authored-By: Dominik Prokop <dominik.prokop@grafana.com>

* Docs: Updates docs according to PR comments

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

package.json

@@ -208,6 +208,7 @@
     "@types/md5": "^2.1.33",
     "@types/react-loadable": "5.5.2",
     "@types/react-virtualized-auto-sizer": "1.0.0",
+    "abortcontroller-polyfill": "1.4.0",
     "angular": "1.6.9",
     "angular-bindonce": "0.3.1",
     "angular-native-dragdrop": "1.2.2",
@@ -267,6 +268,7 @@
     "tether-drop": "https://github.com/torkelo/drop/tarball/master",
     "tinycolor2": "1.4.1",
     "tti-polyfill": "0.2.2",
+    "whatwg-fetch": "3.0.0",
     "xss": "1.0.3"
   },
   "resolutions": {