Support for @defer/@stream directives

Hi there :)
We're using Hasura and it's pretty awesome. We currently tackle the issue of having a very large query with remote joins (for other Graphql api) and we think ```@defer``` and ```@stream``` directives can be suited for solving this. (https://foundation.graphql.org/news/2020/12/08/improving-latency-with-defer-and-stream-directives)
While they may offer less value for complex SQL query (although ```@stream``` might still be useful), it does provide high value when using field relations that are connected to external Graphql apis.
Thanks!