[clang-tools-extra] [clangd] Enable query-based custom checks (PR #216336)

[Peiqi Li via cfe-commits]

voyager-jhk wrote:

> Also, will the docs at https://clangd.llvm.org/ be updates as well?

Yeah, I can update the docs there too.

https://github.com/llvm/llvm-project/pull/216336