Recommend `connect-backbone-to-react` for integrating Backbone data

Hello!

Here, y'all recommend an approach for integrating Backbone models and collections with React and include a code snippet for doing so.

Luckily, this functionality has been achieved using a HoC (like the snippet recommends) in a simple, tested library created by MongoDB called connect-backbone-to-react. We and they (and probably others) have been using the library in production with great success (in our case, for over 6 months).

Recommending connect-backbone-to-react would help devs and projects new to React get up-and-running with React+Backbone quickly and easily. Rather than building their own integration library, they could simply use one that already exists. Also, by centralizing on a solution, the community could collaborate to make the migration from Backbone to React easier and safer for everyone.

connect-backbone-to-react additionally offers a Redux-like provider in BackboneProvider, that many folks may find useful.

Happy to submit a PR to update the docs :). Wanted to check in to get y'all's thoughts first.

Start with the Backbone models section in content/docs/integrating-with-other-libraries.md, linked in the issue, and review the existing integration snippet alongside connect-backbone-to-react and its BackboneProvider documentation. Done means updating the React documentation to recommend the library if maintainers approve, while keeping the integration guidance and links accurate.