[Docs]: Added relevant documentation for manual installation

[hotdogc1017]

What problem does this feature solve?

I'm developing a component library, migrating from vite to rslib (should be vite -> rspack -> rsbuild, and finally found rslib 😄), but the documentation only describes starting with create-rslib, which makes me have to look through the source code to see which dependencies I should use. Consider adding a document similar to rsbuild manual installation.

What does the proposed API look like?

none

[Timeless0911]

Got it, I will add this chapter in [Quick Start].