chore(showcase): add site attejuvonen.fi to site showcase (#13169)

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## Description

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docs/sites.yml

@@ -5233,3 +5233,14 @@
     - Photography
   built_by: Little Wolf Studio
   built_by_url: https://littlewolfstudio.co.uk
+- title: Atte Juvonen - Blog
+  url: https://www.attejuvonen.fi/
+  main_url: https://www.attejuvonen.fi/
+  source_url: https://github.com/baobabKoodaa/blog
+  description: >
+    A blog with streamlined design and smooth UX
+  categories:
+    - Blog
+    - Technology
+    - Web Development
+  featured: false