deps: increase "engines" to "node" : ">= 10.12.0"

Makes npm warn users if they are using an unsupported Node version.

Refs: nodejs#2123

Author: DeeDeeG

package.json

@@ -34,7 +34,7 @@
     "which": "^2.0.2"
   },
   "engines": {
-    "node": ">= 6.0.0"
+    "node": ">= 10.12.0"
   },
   "devDependencies": {
     "bindings": "^1.5.0",