dropping node18 support since its passed its end of life

Author: jshemas

.github/workflows/node.js.yml

@@ -16,7 +16,6 @@ jobs:
       fail-fast: false
       matrix:
         node-version:
-          - 18
           - 20
           - 22
           - 24

package.json

@@ -28,7 +28,7 @@
     "test": "npm run mocha:unit && npm run mocha:int"
   },
   "engines": {
-    "node": ">=18.0.0"
+    "node": ">=20.0.0"
   },
   "author": {
     "name": "Josh Shemas",