Add cheatsheets from devhints.io

Website Link: https://devhints.io/
Repository Link: https://github.com/rstacruz/cheatsheets

This repository contains cheatsheet for various libraries which are missing at cheat.sh, for example lodash, backbone.js etc.

Start with the devhints.io and rstacruz/cheatsheets links in the issue, then inspect cheat.sh's existing cheatsheets to identify how missing libraries such as lodash and Backbone.js are represented. Confirm the desired scope with maintainers before adding entries; done means the selected cheatsheets are available through cheat.sh.

Written by the indexing model from the issue text.