chore(rsc): update package.json for starter-cf-single

[mashaal]

Description

Cloning the starter-cf-single example with degit, it is missing the vite and rsc-html-stream and will not run or build.

Adding these and the project works as expected when running:

npx degit vitejs/vite-plugin-react/packages/plugin-rsc/examples/starter-cf-single starter-cf-single

[hi-ogawa]

As I didn't include it in README.md, this example isn't technically intended to be "degit"-able but it's only for test case. That said, I don't mind adding two dependencies, so I will merge. Thanks!