Idea: fill all available fields in one level

For testing purposes can take some time to write all fields. Would be great if we could somehow fill all available fields in current level of query or mutation... We could use something like "execute mutation" button and use it to prefill all fields.

## Specifications

- GraphQL for VSCode Extension Version: 0.3 Insider
- VSCode Version: GraphQL Insiders
- OS Name: Mac OS X
- OS Version: Big Sur