React is not externaled when optimizing deps

[csr632]

Reproduce:

https://github.com/csr632/test-vite/tree/debug-plugin-react
After optimize, go to node_modules/.vite_opt_cache/styled-components, search for react.development.js in it. You can see react is bundled.

Investigate

When optimizing styled-components, react is resolved into @pika/react/source.development.js:
https://github.com/vitejs/vite-plugin-react/blob/a37f540ab16bfe256273b7719e9432a4b3b4efdf/src/resolver.ts#L7

but the rollup external config is @pika/react

Fix

vitejs/vite#218 and vitejs/vite-plugin-react#5 fix this.
I resolve the rollup external config with resolver before calling rollup to optimize. So that the rollup external config will be @pika/react/source.development.js instead of @pika/react.