Bump minimum supported Node.js version to 14.0.0

Latest version of ESLint no longer supports v12.0.0 that went EOL
in April, 2022

Add Node.js 18.0.0 to CI

.github/workflows/node.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-v: [12.x, 14.x, 16.x]
+        node-v: [14.x, 16.x, 18.x]
     steps:
       - name: Checkout
         uses: actions/checkout@v2