docs: add cargo-wdk preview callout to Cargo Make section in README (#641)

This pull request updates the documentation to inform users about a new
build tool in development for Rust drivers. The most important change is
the addition of a preview notice about the upcoming `cargo-wdk` tool.

Documentation update:

* Added a preview notice in `README.md` announcing the development of
the `cargo-wdk` cargo-extension, which is intended to replace
`cargo-make` as the recommended tool for building Rust drivers, and
encouraged users to try it out and provide feedback.

---------

Signed-off-by: Krishna Kumar Thokala <krishna.thokala2010@gmail.com>
Co-authored-by: Gurinder Singh <frederick.the.fool@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

README.md

@@ -178,6 +178,8 @@ Minimal examples of `WDM`, `KMDF`, and `UMDF` drivers can be found in the [examp
 
 ## Cargo Make
 
+> **Preview:** We are developing a new Cargo extension [`cargo-wdk`](https://crates.io/crates/cargo-wdk) that will replace `cargo-make` as the recommended tool for building Rust drivers. Please try it out and share your feedback.
+
 [`cargo-make`](https://github.com/sagiegurari/cargo-make) is used to facilitate builds using `windows-drivers-rs`, including for executing post-build driver packaging steps.
 
 To execute the default action (build and package driver):