chore: add workflow for testing the build on PRs (#303)

Author: katelynsills

.github/workflows/test-build.yml

@@ -0,0 +1,21 @@
+name: Test the build
+
+# run CI on pushes to master, and on all PRs (even the ones that target other
+# branches)
+
+on:
+ push:
+   branches: [master]
+ pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: Install and Build
+      run: |
+        npm install
+        npm run docs:build