ci: test using Node.js 18

Author: iiroj

.github/workflows/main.yml

@@ -40,12 +40,12 @@ jobs:
   test:
     strategy:
       matrix:
-        # Test with Node.js v12 (LTS), v14 (LTS), v16 (LTS), and 17 (Current)
+        # Test with Node.js v12 (LTS), v14 (LTS), v16 (LTS), and 18 (Current)
         node:
           - 12
           - 14
           - 16
-          - 17
+          - 18
         # Test with Ubuntu, macOS, and Windows
         os:
           - ubuntu-latest