Add additional resources, project ideas and open source to React guide

We need to add the following to the current React guide
- [ ] Additional resources for learning React (books, awesome list, courses etc)
- [ ] Complete project ideas to apply all the concepts listed in the guide
- [ ] Open Source projects built on React (including React) to contribute to

CC : @M-ZubairAhmed and @aravindballa

Start by locating and reading the current React guide. Add learning resources, complete project ideas covering the guide's concepts, and React open-source projects—including React itself—for contribution; the work is done when all three requested sections are included and checked for relevance.

Written by the indexing model from the issue text.