meta: run ci on node 18 (#305)

- drop node 15 and 17 (#305 (comment))

.github/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
     name: Lint
     strategy:
       matrix:
-        node-version: [16.x]
+        node-version: [18]
         os: [ubuntu-latest]
     runs-on: ${{ matrix.os }}
     continue-on-error: true
@@ -29,7 +29,7 @@ jobs:
     name: Test (Library)
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 15.x, 16.x, 17.x]
+        node-version: [12, 14, 16, 18]
         os: [ubuntu-latest, windows-latest, macos-latest]
     runs-on: ${{ matrix.os }}
     continue-on-error: true
@@ -48,7 +48,7 @@ jobs:
     name: Test (External)
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 15.x, 16.x, 17.x]
+        node-version: [12, 14, 16, 18]
         os: [ubuntu-latest]
     runs-on: ${{ matrix.os }}
     continue-on-error: true
@@ -87,7 +87,7 @@ jobs:
         uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
-          node-version: 16
+          node-version: 18
           registry-url: https://registry.npmjs.org/
       - name: Install dependencies
         run: npm ci