Fix nextConfig type

[CodeWithShreyans]

Please describe the changes this PR makes and why it should be merged:

Type errors occur in users' nextConfig if any options apart from the following are used:

nextConfig: {
    appDir?: boolean;
    basePath?: string;
    webpack?: (config: Record<string, any>, options: any) => any;
  }

This PR uses the NextConfig type from next to fix this issue.

Status

• [x] Code changes have been tested against prettier, or there are no code changes
• [x] I know how to update typings and have done so, or typings don't need updating

Semantic versioning classification:

• [x] This PR changes the codebase
  • [ ] This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
  • [x] This PR changes the internal workings with no modifications to the external API (bug fixes, performance improvements)
• [ ] This PR only includes non-code changes, like changes to documentation, README, etc.

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[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs within the next 7 days.

[CodeWithShreyans]

@aidenybai Could you take a look?

[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs within the next 7 days.