For those struggling to get this working. It does actually work :)

1) Add the browser extension.
2) Add `connectToDevTools: true` property to your ApolloClient instance.
3) Find the apollo tab on your browser dev tools - as you would react dev tools etc.

This is a really useful plugin for anyone working with Apollo GraphQL.

Mozilla Addons team, please please review and approve plugin v3.x

Thanks for all the work getting this resubmitted!