build: mark latest supported version as Node 16

BREAKING CHANGE: Explicitely drops support for Node.js 14 and 15

Author: Addono

package.json

@@ -18,7 +18,7 @@
     "src"
   ],
   "engines": {
-    "node": ">=14"
+    "node": ">=16"
   },
   "scripts": {
     "start": "tsdx watch",