docs(graphql): added jsdoc for debug and introspection. closes #3142

[aarontravass]

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
• 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?

Added debug and introspection in GqlModuleOptions. Added relevant jsDocs for improved developer experience. Closes #3142

Issue Number: #3142

What is the new behavior?

Auto-complete will now work in supported editors and developers will have an idea what debug and introspection are without referring to nest/apollo docs.

Does this PR introduce a breaking change?

• Yes
• No

Other information