docs: rust: add command line to rust-analyzer section

Add command line to rust-analyzer section for convenience purposes.

Signed-off-by: Guillaume Plourde <gplourde@protonmail.com>
Link: https://lore.kernel.org/r/y4jBalhfESeCZDShmVaGwrdlIRoIHroqNVUUYLck6qGNwB5e7wbIJO5DoiLBTPpTNYtdneWRODjhXwlIl9VzokqxffdNU7y__1wIa7BBl94=@protonmail.com


[ Fixed indentation to tab and reworded title. ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>