[Relay] Consider adding the new relay-devtools extension?

Thanks for a great tool!

Recently mentions of relay-devtools have appeared [in the Relay Modern docs](https://github.com/facebook/relay/blob/master/docs/modern/Debugging.md#debugging-visually). While the repos are not public yet, [the Chrome extension](https://chrome.google.com/webstore/detail/relay-devtools/oppikflppfjfdpjimpdadhelffjpciba) can already be installed.

I was hoping that you may consider including that already or, if not, if you could point me at where I need to update code to include this extension myself?