fix: return partial config from vite config hook

[stevezhu]

Because vite deeply merges configs, returning the entire config from the config hook should be avoided. Instead return the partial config with alias entries.

Reference: https://vitejs.dev/guide/api-plugin.html#config

[stevezhu]

This was causing issues in storybookjs/storybook#20643

[IanVS]

I tested this change locally by replicating in my node_modules, and it does indeed fix the HMR issue in dev. @crcong would you consider merging and releasing a new version so that we can continue to use this plugin in Storybook? Thanks for your hard work here, it was just what we needed (if this issue can be fixed).

[stevezhu]

Related original issue #5

[crcong]

Thanks!