chore(showcase): Add effico.ltd (gatsbyjs#24268)

Co-authored-by: gatsbybot <mathews.kyle+gatsbybot@gmail.com>
Co-authored-by: Lennart <lekoarts@gmail.com>

docs/sites.yml

@@ -10739,6 +10739,17 @@
   built_by: Thanawat Gulati
   built_by_url: https://twitter.com/mjamesvevo
   featured: false
+- title: Effico Ltd
+  main_url: https://www.effico.ltd
+  url: https://www.effico.ltd
+  source_url: https://github.com/Zellement/effico
+  description: >
+    Commercial and domestic electrical contractors.
+  categories:
+    - Business
+  built_by: Dan Farrow
+  built_by_url: https://www.zellement.com
+  featured: false
 - title: Sheringham Flooring
   main_url: https://www.sheringhamflooring.com
   url: https://www.sheringhamflooring.com