chore(package): add script clean that removes dist directory

Author: remarkablemark

package.json

@@ -6,6 +6,7 @@
   "main": "src/index.js",
   "scripts": {
     "build": "mkdir -p dist && cp src/embed.js dist/embed.js && uglifyjs src/embed.js --output dist/embed.min.js --compress --mangle",
+    "clean": "rm -rf dist",
     "commitmsg": "commitlint -e $GIT_PARAMS",
     "lint": "eslint --ignore-path .gitignore .",
     "lint:fix": "npm run lint -- --fix",