cicd: test against LTS node versions, drop 12, add 18.

Author: Codex-

.github/workflows/build.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 16.x]
+        node-version: [14.x, 16.x, 18.x]
     steps:
       - uses: actions/checkout@v2
       - name: Use Node.js ${{ matrix.node-version }}