Script to check licenses (#3757)

* Add script task to check licenses of all dependenies

package.json

@@ -27,6 +27,7 @@
     "build:langfiles": "gulp buildLangfiles",
     "build:uncompressed": "gulp buildUncompressed",
     "bump": "npm version 3.$(date +'%Y%m%d').0",
+    "license": "gulp checkLicenses",
     "lint": "eslint .",
     "package": "gulp package",
     "postversion": "gulp postversion",
@@ -57,7 +58,6 @@
     "concurrently": "^4.1.2",
     "eslint": "^5.13.0",
     "eslint-plugin-es5": "^1.4.1",
-    "fs": "0.0.1-security",
     "google-closure-compiler": "^20200101.0.0",
     "google-closure-deps": "^20200101.0.0",
     "gulp": "^4.0.2",
@@ -69,6 +69,7 @@
     "gulp-replace": "^1.0.0",
     "gulp-umd": "^2.0.0",
     "jshint": "^2.10.2",
+    "js-green-licenses": "^1.1.0",
     "mocha": "^6.1.4",
     "pixelmatch": "^4.0.2",
     "pngjs": "^3.4.0",