Gives an overview of how to build and use the shader debugging functionality.

Bug: b/148373999
Change-Id: Ia884379aac03bf40b27c298a909ea2961fe643aa
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/40531Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>