Introspection command should return sorted results.

[tbrannam]

I'd like to use the introspection command to track schema changes over time in a git repo. It appears the schema output is likely dependent on the order of the resolvers added.

To make for a more consistent output - it would be nice if the introspection command dictated some fixed sort order for the output file - this would help with folks that are looking at diffs of the schema over time.

[kamilkisiela]

#1831 thank you for the PR!