Add SWRInfiniteMutatorOptions type to export

[ludwigbacklund]

When using "moduleResolution": "Bundler" in tsconfig.json for a TypeScript project, and implicitly referencing SWRInfiniteMutatorOptions you get this error:

Exported variable '<redacted>' has or is using name 'SWRInfiniteMutatorOptions' from external module "/path/node_modules/swr/dist/infinite/index" but cannot be named.ts(4023)

These errors can be resolved by explicitly exporting these implicitly references types from swr.

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[koba04]

👍 LGTM, thank you!