Include graphqurl inside docker images

### Is your proposal related to a problem?

It would be useful to have access to [graphqurl](https://github.com/hasura/graphqurl) directly from within the hasura docker images, not unlike psql inside postgres images.

### Describe the solution you'd like

After opening a shell into a hasura container, I want to type graphqurl and be able to connect to the local instance, either to execute some graphql queries or to export the schema.

Very important: I use both the standard and `.cli-migrations` images so if graphqurl does get included, I want it in all possible images.

### Describe alternatives you've considered

`npm install graphqurl`, which absolutely sucks / isn't an option when you're debugging something deployed on premises.

Start by locating the Docker image build definitions for the standard and .cli-migrations images, then determine where an additional CLI dependency belongs. Done means graphqurl is available from a shell in every requested image and can connect to the local instance for queries or schema export.

Written by the indexing model from the issue text.