chore(showcase): add PicPick to showcase (#13279)

Added https://picpick.app/ to showcase.

This site has been developed using gatsby since early 2018, but I recently upgraded to v2 with plugin https://github.com/wiziple/gatsby-plugin-intl to support 15 different languages. 😄

<!--
  Have any questions? Check out the contributing docs at https://gatsby.dev/contribute, or
  ask in this Pull Request and a Gatsby maintainer will be happy to help :)
-->

## Description

<!-- Write a brief description of the changes introduced by this PR -->

## Related Issues

<!--
  Link to the issue that is fixed by this PR (if there is one)
  e.g. Fixes #1234, Addresses #1234, Related to #1234, etc.
-->

docs/sites.yml

@@ -5280,3 +5280,15 @@
   built_by: Maitrik Patel
   built_by_url: https://www.maitrikpatel.com/
   featured: false
+- title: PicPick
+  url: https://picpick.app/
+  main_url: https://picpick.app/
+  description: >
+    All-in-one Graphic Design Tool, Screen Capture Software, Image Editor, Color Picker, Pixel Ruler and More
+  categories:
+    - Productivity
+    - App
+    - Technology
+  built_by: NGWIN
+  built_by_url: https://picpick.app/
+  featured: false