fix: increase Node minimum version requirement to 10.12.0 (twilio#91)

Relates to twilio/twilio-cli-core#90

[mkdirSync](https://nodejs.org/api/fs.html#fs_fs_mkdirsync_path_options) is used with the recursive option which wasn't added until 10.12.0 so we should enforce this as the minimum version.

package.json

@@ -44,7 +44,7 @@
     "tmp": "^0.1.0"
   },
   "engines": {
-    "node": ">=10.0.0"
+    "node": ">=10.12.0"
   },
   "files": [
     "/bin",