docs: fix SWC configuration link

[Lovlace777]

Summary

• Fixes the README SWC configuration documentation link reported in [Docs] Broken link #28.
• Updates the URL to the current Storybook main config SWC docs route.
• Adds a patch changeset because README is included in the published package.

Validation

• curl.exe -L -I https://storybook.js.org/docs/api/main-config-swc returned HTTP 404.
• curl.exe -L -I https://storybook.js.org/docs/api/main-config/main-config-swc returned HTTP 200.
• COREPACK_INTEGRITY_KEYS=0 corepack pnpm install --frozen-lockfile passed.
• COREPACK_INTEGRITY_KEYS=0 corepack pnpm build passed.
• COREPACK_INTEGRITY_KEYS=0 corepack pnpm changeset status --since=main passed and detected a patch bump.
• git diff --cached --check passed with Windows line-ending warnings only.
• COREPACK_INTEGRITY_KEYS=0 corepack pnpm format and COREPACK_INTEGRITY_KEYS=0 corepack pnpm check:ci were attempted locally, but failed on untouched src files because the Windows working tree contains CRLF line endings that Biome would normalize to LF.

Notes

• Closes [Docs] Broken link #28.
• No runtime behavior changes.
• No follow-up work expected.