feat(): Add sortSchema option

[mattleff]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #993 (closes #993)

What is the new behavior?

Providing the sortSchema option to the GraphQLModule will sort the schema lexicographically.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

I don't consider this to be a breaking change.

Other information

[kamilmysliwiec]

Would you like to create a PR to the docs with this feature? Maybe in this section https://docs.nestjs.com/graphql/quick-start#code-first

[mattleff]

@kamilmysliwiec I've added a PR: nestjs/docs.nestjs.com#1323.