Support `documentVariableSuffix` when using `documentMode: 'external'`

[abrenneke]

Description

This implements the fix suggested in https://github.com/dotansimha/graphql-code-generator-community/issues/141

This is correctly appending Document to the operations externally imported for me, which is fixing all compiler errors.

If there's a better way to support this, I'm open to suggestions, but this is working well for me. Will add tests etc if requested.

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Tested with a yarn patch on personal code.

Checklist:

• [ ] I have followed the CONTRIBUTING doc and the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 6c8b0dbfd405712610f52957ba913d64312a83fb

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR