Use Node 12 in Playwright job runner.

Author: onurtemizkan

.github/workflows/build.yml

@@ -312,6 +312,13 @@ jobs:
         uses: actions/checkout@v2
       - name: Set up Node
         uses: actions/setup-node@v1
+        with:
+          # The only danger with Ember in terms of Node versions is that the build tool, ember-cli, won't work if Node
+          # is too old. Since Oct 2019, Node 10 has been the oldest version supported by ember-cli, so test against
+          # that. If it passes, newer versions of Node should also be fine. This saves us from having to run the Ember
+          # tests in our Node matrix above.
+          node-version: '12'
+          fetch-depth: 0
       - name: Check dependency cache
         uses: actions/cache@v2
         with: