Add contents section to case study document

Added a contents section with links to various topics related to the commerce platform modernization case study.

Author: Don-Damiano

src/content/en-case-studies/commerce-platform-modernization.mdx

@@ -19,6 +19,19 @@ links:
 
 import GalleryLightbox from "../../components/GalleryLightbox.astro";
 
+## Contents
+
+- [System Context](#system-context)
+- [Why a Monolith Was the Right Decision 10 Years Ago](#why-a-monolith-was-the-right-decision-10-years-ago)
+- [Why Modernization Is Necessary Today](#why-modernization-is-necessary-today)
+- [Transformation Strategy](#transformation-strategy)
+- [Modernization Progress](#modernization-progress-real-changes)
+- [Current State](#current-state)
+- [Current Outcome](#current-outcome)
+- [Architecture Showcase](#architecture-showcase-github)
+
+---
+
 ## System Context
 
 This project concerns the modernization of **Comers**, a proprietary online sales management platform available at `comers.app`, designed and continuously developed by our team for approximately 10 years.