devops: drop Node.js 12

Author: mxschmitt

.github/workflows/nodejs.yml

@@ -10,7 +10,7 @@ jobs:
       fail-fast: false
       matrix:
         platform: [ubuntu-latest, windows-latest]
-        node: [12.x, 14.x]
+        node: [14.x, 16.x, 18.x]
     runs-on: ${{ matrix.platform }}
     steps:
     - uses: actions/checkout@v2