feat(build): support cacheDir

[shigma]

I recommend keeping default vite cache directory under .vitepress for the following reasons:

• When the codebase its depends on vite, cache stored in node_modules/.vite would overwrite each other, causing unexpected and undetectable problems
• vuepress next already has similar configuration

[kiaking]

I think the idea is nice. @shigma do you think you can resolve the failing tests?

[shigma]

@kiaking Thanks for your attention.

The failing tests can be solved by vitejs/vite#10242. If it can not be accepted, we can still manully add ignore pattern here in vitepress. It is just better to have it in vite from my perspective.

[kiaking]

Ah, I see. Thanks! OK, let's wait for Vite side on this 👍