Add note about using "example.com" as an example domain

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/prerequisites.md

@@ -4,6 +4,8 @@
 
 To install Matrix services using this Ansible playbook, you need to prepare several requirements both on your local computer (where you will run the playbook to configure the server) and the server (where the playbook will install the Matrix services for you). **These requirements need to be set up manually** before proceeding to the next step.
 
+We will be using `example.com` as the domain in the following instruction. Please remember to replace it with your own domain before running any commands.
+
 ## Your local computer
 
 - [Ansible](http://ansible.com/) program. It's used to run this playbook and configures your server for you. Take a look at [our guide about Ansible](ansible.md) for more information, as well as [version requirements](ansible.md#supported-ansible-versions) and alternative ways to run Ansible.

docs/quick-start.md

@@ -2,7 +2,9 @@
 
 This page explains how to use this Ansible book in order to install Matrix services on your server with minimum core services.
 
-By following the instruction on this page, you will set up **your own Matrix server**, **your user account** like `@user:example.com` (where `example.com` is the "base domain") on the server, and **self-hosted Matrix client**, [Element Web](configuring-playbook-client-element-web.md) with the default subdomain at `element.example.com`.
+By following the instruction on this page, you will set up **your own Matrix server**, **your user account** like `@user:example.com` on the server, and **self-hosted Matrix client**, [Element Web](configuring-playbook-client-element-web.md) with the default subdomain at `element.example.com`.
+
+We will be using `example.com` as the "base domain" in the following instruction. Please remember to replace it with your own domain before running any commands.
 
 ## Prerequisites