fix: Use browserslist-config

We were installing browserslist-config but not declaring it.  This had
the effect that webpack - and likely others - were not using it.

package.json

@@ -6,6 +6,9 @@
     "type": "git",
     "url": "git+https://github.com/edx/frontend-app-ora-grading.git"
   },
+  "browserslist": [
+    "extends @edx/browserslist-config"
+  ],
   "scripts": {
     "build": "fedx-scripts webpack",
     "i18n_extract": "fedx-scripts formatjs extract",
@@ -72,7 +75,7 @@
     "whatwg-fetch": "^3.6.2"
   },
   "devDependencies": {
-    "@edx/browserslist-config": "^1.2.0",
+    "@edx/browserslist-config": "^1.3.0",
     "@edx/react-unit-test-utils": "3.0.0",
     "@edx/reactifex": "^2.1.1",
     "@openedx/frontend-build": "14.0.3",