Drop support for Node.js 16, require >=18

Since Node.js 16 is no longer supported upstream, and is starting to be
unsupported by some projects (e.g. octokit) there's no need for us to
continue to support it.

Signed-off-by: Kevin Locke <[email protected]>

Author: kevinoid

.github/workflows/node.js.yml

@@ -86,7 +86,7 @@ jobs:
         - ubuntu-latest
         - windows-latest
         node:
-        - '16'
+        - '18'
         - latest
         exclude:
         # Exclude os/version already run in test-primary

package.json

@@ -75,7 +75,7 @@
     "rimraf": "^5.0.0"
   },
   "engines": {
-    "node": ">=16",
+    "node": ">=18",
     "npm": ">=1.3.7"
   },
   "david": {