Update changelog with changes since 2026.4.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: C4ptainCrunch

CHANGELOG.md

@@ -2,6 +2,16 @@
 
 This page tries to contain all use facing changes made on DocHub.
 
+# Unreleased
+
+ * Add a moderation system: moderators can now edit any document
+ * Add a representative request form for students to apply for moderator rights
+ * Add a moderation tree view showing who promoted whom (chain of trust)
+ * Add a public moderation transparency log visible to all logged-in users
+ * Add a public page explaining the moderation system
+ * Fix catalog navigation flicker (#365)
+ * Fix bulk upload Turbo error (#377)
+
 # 2026.4.0 
 
  * Add a institutional disclaimer and contribution call on the login page