Document pulling the sudo password from pass via the passwordstore lookup

Based on https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/4219 by @mcnesium

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/installing.md

@@ -41,6 +41,8 @@ If you **don't** use SSH keys for authentication, but rather a regular password,
 
 If you **do** use SSH keys for authentication, **and** use a non-root user to *become* root (sudo), you may need to add `-K` (`--ask-become-pass`) to all Ansible commands.
 
+Instead of typing the sudo password on each run (`-K`) or storing it in plain text in the inventory hosts file, you can also pull it from the [pass](https://www.passwordstore.org/) password manager by adding `ansible_become_password='{{ lookup("community.general.passwordstore", "path/to/password") }}'` to your host line. See the [passwordstore lookup documentation](https://docs.ansible.com/ansible/latest/collections/community/general/passwordstore_lookup.html) for more details.
+
 There 2 ways to start the installation process — depending on whether you're [Installing a brand new server (without importing data)](#installing-a-brand-new-server-without-importing-data) or [Installing a server into which you'll import old data](#installing-a-server-into-which-youll-import-old-data).
 
 **Note**: if you are migrating from an old server to a new one, take a look at [this guide](maintenance-migrating.md) instead. This is an easier and more straightforward way than installing a server and importing old data into it.