[docs] Template moulding in docs/platform and index improvement (#3663)

docs/templates/section_overview_template.mdx

@@ -36,12 +36,12 @@ icon: "compass"
   Start with [Quickstart link] if you’re new, then choose a deeper topic below.
 </Info>
 
-<!-- Optional: delete if not needed -->
+{/* Optional: delete if not needed */}
 ```mermaid
 graph LR
-  A[Get set up] --> B[Learn concepts]
-  B --> C[Build workflows]
-  C --> D[Support & scale]
+  A[Get set up] */} B[Learn concepts]
+  B */} C[Build workflows]
+  C */} D[Support & scale]
 ```
 
 ## Choose your path
@@ -73,7 +73,7 @@ graph LR
 
 ## Keep going
 
-<!-- DEBUG: verify CTA targets -->
+{/* DEBUG: verify CTA targets */}
 
 <CardGroup cols={2}>
   <Card