Add placeholder module

Adds a simple placeholder Rust module to allow the build pipelines to
pass. They expect a Cargo.toml file to be present in the repo.

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>

Cargo.toml

@@ -0,0 +1,4 @@
+[package]
+name = "hid_report_descriptor_parser"
+version = "0.1.0"
+edition = "2021"

src/lib.rs

@@ -0,0 +1,4 @@
+#![no_std]
+
+#[allow(dead_code)]
+fn placeholder() {}