Adding the Compiler Annotation guide to work-in-progress (#943)

Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>
Signed-off-by: Thomas Nyman <thomasnyman@users.noreply.github.com>
Co-authored-by: Thomas Nyman <thomasnyman@users.noreply.github.com>

Author: gkunz

docs/index.md

@@ -39,6 +39,7 @@ Examples of ongoing work include:
 
 * [Secure Coding One Stop Shop for Python](Secure-Coding-Guide-for-Python/readme.md)
 * [Security Focused Guide for AI Code Assistant Instructions](https://best.openssf.org/Security-Focused-Guide-for-AI-Code-Assistant-Instructions)
+* [Compiler Annotations for C and C++](Compiler-Hardening-Guides/Compiler-Annotations-for-C-and-C++.md)
 
 We typically use the [Simplest Possible Process (SPP)](https://best.openssf.org/spp/Simplest-Possible-Process) to publish our results on the web.