fix(react-router): pin react-router type def files - #586

Thanks for this! It helped a lot in showing what the problem was.

Rather than pinning to a specific version of dependencies, I'd made a slightly different fix: f8714e9. This uses tsconfig.json's paths field to tell TypeScript which @types package is the official one for react/redux/history, rather than letting it use its default behaviour of combining all matching type definitions (which causes the "duplicate identifier" issue).

I prefer not to pin dependencies exactly to minor versions, because at some point, somebody will have some reason why they need to update to a newer version, but then they'd run into the original issue again and we wouldn't necessarily have any solution. Sometimes we might be forced to pin dependencies that precisely but on this occasion it seems we have an alternative :) Hope that's OK.

Good idea! 👍