Section on rust-analyzer should recommend enabling seperate cargo directories

> Rust-analyzer › Cargo: Target Dir
> Optional path to a rust-analyzer specific target directory. This prevents rust-analyzer's cargo check and initial build-script and proc-macro building from locking the Cargo.lock at the expense of duplicating build artifacts.
> Set to true to use a subdirectory of the existing target directory or set to a path relative to the workspace to use that path.

This is a huge QoL / iteration speed improvement. It should be mentioned right after we talk about `rust-analyzer`. Call out both the pros and cons.

Locate the website section that discusses rust-analyzer and read the surrounding guidance. Add a recommendation for separate Cargo target directories, including the stated iteration-speed benefits and the trade-offs. Done means the recommendation appears immediately after the rust-analyzer discussion and covers both pros and cons.

Written by the indexing model from the issue text.