ci(actions): run builds for all supported Node versions

Author: jrolfs

.github/workflows/build.yml

@@ -21,9 +21,12 @@ jobs:
           concurrent_skipping: same_content_newer
 
   build:
-    name: Build + Test + Release
+    name: Build + Test + Release / Node ${{ matrix.node }}
     runs-on: ubuntu-latest
     if: ${{ needs.deduplicate.outputs.should_skip != 'true' }}
+    strategy:
+      matrix:
+        node: ['12', '14', '16']
 
     steps:
       - name: Get Yarn cache path
@@ -36,7 +39,7 @@ jobs:
       - name: Setup node
         uses: actions/setup-node@master
         with:
-          node-version: 14.x
+          node-version: ${{ matrix.node }}
 
       - name: Load Yarn cache
         uses: actions/cache@v2