typescript-urql plugin ignores `documentMode`

**Describe the bug**
typescript-urql plugin ignores `documentMode` `importDocumentNodeExternallyFrom` and `importOperationTypesFrom` settings

**To Reproduce**
```
schema: schema.graphql
documents: document.graphql
generates:
types.ts:
plugins:
- typescript
- typescript-operations
urql.ts:
plugins:
- "typescript-urql"
config:
documentMode: "external"
importDocumentNodeExternallyFrom: "./types.ts"
```

As you can see here the generated file ignores the external document mode.
https://codesandbox.io/s/confident-dream-l0sd5?file=/urql.ts

**Expected behavior**
To have the generated urql hooks to reference the external type file

This issue looks like the same from https://github.com/dotansimha/graphql-code-generator/pull/4765 and I've used the code from there to fix this issue