docs: Add Resources tab listing tutorials created by the community

[nickscamara]

Suggestions to improve docs, user experience, and community engagement:

• Add a resources tab that has links to external tutorials/resources/etc that the community creates to help teach react-sweet-state.

I went ahead and added an "External Tutorials" page featuring an interactive tutorial. This will help potential users to better understand the framework allowing them to try for themselves a real use case without leaving the web. The tutorial itself provides code walkthroughs and an interactive sandbox environment with a counter app example adapted from the docs.

Hope you like this add-on and would love any feedback.

[atlassian-cla-bot[bot]]

Hooray! All contributors have signed the CLA.

[nickscamara]

@albertogasparin let me know if this is helpful - would love to keep contributing.

[nickscamara]

Any updates on this? Thank you