Update p5.5.yaml

Author: eltapir

src/content/libraries/en/p5.5.yaml

@@ -1,6 +1,6 @@
 name: p5.5
 description: Add UI to p5.js and other goodies
-category: User Interface
+category: ui
 sourceUrl: https://github.com/eltapir/p5.5
 featuredImage: ../images/p5.5.jpg
 featuredImageAlt: Screenshot of p5.5.js