Point customers to the correct SPA example code.

Please spend some time to update some documentation, links, repo's on behalf of clarity for clients where to find examples.

1. https://www.npmjs.com/package/@bloomreach/react-sdk has as Repository link the outdated https://code.onehippo.org/cms-community/bloomreach-spa-sdk
2. we have an outdated repo https://github.com/bloomreach/experience-react-sdk which is pinned on /bloomreach
3. we have an outdated repo https://github.com/bloomreach/brxm-react-spa

At least #1 is a quick bugfix, maybe we should drop the outdated repos.