Add node 18 to CI and remove node 12

Author: octet-stream

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest, windows-latest]
-        node: [12.x, 14.x, 16.x, 17.x]
+        node: [14.x, 16.x, 18.x]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2