fix(post): Added ceph instructions for proxmox

Author: timothystewart6

_posts/2020-11-28-first-11-things-proxmox.md

@@ -66,6 +66,15 @@ Create a file at `/etc/apt/sources.list.d/pve-no-enterprise.list` with the follo
 deb http://download.proxmox.com/debian/pve bookworm pve-no-subscription
 ```
 
+If you are using ceph
+
+Create a file at `/etc/apt/sources.list.d/ceph.list` with the following contents:
+
+```bash
+# not for production use
+deb http://download.proxmox.com/debian/ceph-quincy bookworm no-subscription
+```
+
 _If you're looking to upgrade to Proxmox 8, [see this post](/posts/upgrade-proxmox-to-8/)_
 
 Run