Check subgraph status before loading the content

[stecb]

As the subgraph can be either indexing or in an error state, we want to promptly warn the users and avoid having an inconsistent state across the dapp.

We could add an "interceptor" and before every request to subgraph check if its status is ok. OR, we can just do a check initially at loading time. We will figure it out.

[stecb]

Closing in favor of https://github.com/NeokingdomDAO/dapp/issues/87