docs: show how to use new apt repo

docs/install/linux.md

@@ -79,6 +79,22 @@ $ ~/bin/wezterm
 
 * Configuration instructions can be [found here](../config/files.md)
 
+## Installing on Ubuntu
+
+Nightly builds are now available in a hosted APT repo.  You can configure your system to
+use that APT repo by following these steps:
+
+```console
+$ curl -fsSL https://apt.fury.io/wez/gpg.key | sudo gpg --yes --dearmor -o /usr/share/keyrings/wezterm-fury.gpg
+$ echo 'deb [arch=all signed-by=/usr/share/keyrings/wezterm-fury.gpg] https://apt.fury.io/wez/ * *' | sudo tee /etc/apt/sources.list.d/wezterm.list
+```
+
+Now you can install wezterm:
+
+```console
+$ sudo apt install wezterm-nightly
+```
+
 ## Installing on Ubuntu and Debian-based Systems
 
 The CI system builds `.deb` files for a variety of Ubuntu and Debian distributions.