chore: add 'npm run bump'

package.json

@@ -4,6 +4,7 @@
   "description": "The \"certbot\" storage strategy for Greenlock.js",
   "main": "index.js",
   "scripts": {
+    "bump": "npm version -m \"chore(release): bump to v%s\"",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "repository": {