Merge pull request #23540 from vvoland/ubuntu-questing

engine/install: Add Ubuntu 25.10

Author: thaJeztah

content/manuals/engine/install/ubuntu.md

@@ -51,6 +51,7 @@ To get started with Docker Engine on Ubuntu, make sure you
 To install Docker Engine, you need the 64-bit version of one of these Ubuntu
 versions:
 
+- Ubuntu Questing 25.10
 - Ubuntu Plucky 25.04
 - Ubuntu Noble 24.04 (LTS)
 - Ubuntu Jammy 22.04 (LTS)