chore: add release script that uses --tag for npm publish for 4.x releases

Fix #6063

Author: vkarpov15

package.json

@@ -77,6 +77,8 @@
     "install-browser": "npm install `node format_deps.js`",
     "lint": "eslint . --quiet",
     "nsp": "nsp check",
+    "release": "git push origin master --tags && npm publish",
+    "release-legacy": "git push origin 4.x --tags && npm publish --tag 4.x",
     "test": "mocha test/*.test.js test/**/*.test.js",
     "test-cov": "istanbul cover --report text --report html _mocha test/*.test.js"
   },

release-items.md

@@ -5,7 +5,7 @@
 3.  update History.md using `git changelog` or similar. Add #<TICKET_NUMBER> as well as a link to the github user who fixed it if applicable.
 4.  git commit -a -m 'release x.x.x'
 5.  git tag x.x.x
-6.  git push origin BRANCH --tags && npm publish
+6.  `npm run release`, or `npm run release-legacy` for 4.x
 7.  update mongoosejs.com (see "updating the website" below)
 8.  tweet changelog link from [@mongoosejs](https://twitter.com/mongoosejs)
 9.  Announce on mongoosejsteam slack channel