message: explain arument passing in the docs
diff: @@ -48,6 +48,13 @@ Now you can run your project in Miri:
  3. If you have a binary project, you can run it through Miri using `cargo
  +nightly miri run`.
  +You can pass arguments to Miri after the first `--`, and pass arguments to the
  +interpreted program or test suite after the second `--`. For example, `cargo
  ++nightly miri run -- -Zmiri-disable-validation` runs the program without
  +validation of basic type invariants and references. `cargo +nightly miri test
  +-- -- filter` passes `filter` to the test suite the same way `cargo test filter`
  +would.
  +
  When running code via `cargo miri`, the `miri` config flag is set. You can
  use this to exclude test cases that will fail under Miri because they do things
  Miri does not support:
  