build!: update library to use Node 12 (#356)

* build!: Update library to use Node 12

Author: sofisl

datalabeling/package.json

@@ -4,7 +4,7 @@
   "license": "Apache-2.0",
   "author": "Google LLC",
   "engines": {
-    "node": ">=10"
+    "node": ">=12.0.0"
   },
   "files": [
     "*.js",
@@ -20,4 +20,4 @@
     "chai": "^4.2.0",
     "mocha": "^8.0.0"
   }
-}
+}