chore(showcase): add Supremekun.com (#12585)

## Description

Add supremekun.com to the app showcase list. 
Supremekun is an online marketplace app for streetwear fashions.

docs/sites.yml

@@ -4954,6 +4954,17 @@
   built_by: d:code:it
   built_by_url: https://dcodeit.com
   featured: false
+- title: SupremeKun - Street Fashion Marketplace and News
+  url: https://supremekun.com
+  main_url: https://supremekun.com
+  description: >
+    Street Fashion Marketplace and News
+  categories:
+    - Marketplace
+    - News
+    - Web Development
+  built_by: allanjiang
+  built_by_url: https://allanjiang.com
 - title: Chase Ohlson
   url: https://chaseohlson.com
   main_url: https://chaseohlson.com