Crate doc of `payload_procedure` is outdated

[Chaoses-Ib]

#16 changed payload_procedure! to be a proc macro, but looks like the crate doc hasn't been updated: https://docs.rs/dll-syringe/0.17.1/dll_syringe/#remotepayloadprocedure

The old code will cause a confusing error that payload_procedure doesn't exist:

error[E0433]: failed to resolve: could not find `payload_procedure` in `dll_syringe`
 --> ib-shell-item\examples\hook.rs:1:14
  |
1 | dll_syringe::payload_procedure! {
  |              ^^^^^^^^^^^^^^^^^ could not find `payload_procedure` in `dll_syringe`

For more information about this error, try `rustc --explain E0433`.
error: could not compile `ib-shell-item` (example "hook") due to 1 previous error

[OpenByteDev]

This is already fixed in the current master version, just hasnt been published yet.