NextJS: Apply next config webpack function

[ShaunEvening]

What I did

• Apply webpack function from next config if it exists to the storybook webpack config

How to test

Checklist

• [ ] Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• [ ] Make sure to add/update documentation regarding your changes
• [ ] If you are deprecating/removing a feature, make sure to update MIGRATION.MD

Maintainers

• [ ] When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts
• [ ] Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "build", "documentation", "maintenance", "dependencies", "other"]

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[ndelangen]

@Integrayshaun do you plan to continue this PR?

Can you consult with @valentinpalkovic, if so. Or close, if not.

🙏