add trombone article

Author: larsrh

_data/projects.yml

@@ -1,3 +1,8 @@
+- date: 2026-04-01
+  link: "https://unnamed.website/posts/3d-printing-trombone/"
+  title: "3D-printing a Trombone"
+  abstract: "Building a perfectly playable plastic trombone for only $30"
+  author: "Anthony Wang"
 - date: 2026-04-01
   link: "https://jameswpm.github.io/post/1001-albums-experience/"
   title: "I listened to the 1001 (?) albums I should listen to before I die"