chore: add checklist to verify the supported graphql types

[sundersc]

Description of changes

Add a checklist step to verify the supported graphql types to the PR template.

Codegen Paramaters Changed or Added

NA

Issue #, if available

NA

Description of how you validated changes

NA

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• Breaking changes to existing customers are released behind a feature flag or major version update
• Changes are tested using sample applications for all relevant platforms (iOS/android/flutter/Javascript) that use the feature added/modified
• Changes are tested on windows. Some Node functions (such as path) behave differently on windows.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.