Document `make roles` some more

Improves:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2232
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2217#issuecomment-1304366791

CHANGELOG.md

@@ -16,7 +16,7 @@ We're doing this for greater code-reuse (across Ansible playbooks, including our
 
 Some variable names will change during the transition to having more and more external (galaxy) roles. There's a new `custom/matrix_playbook_migration` role added to the playbook which will tell you about these changes each time you run the playbook.
 
-From now on, every time you update the playbook (well, every time the `requirements.yml` file changes), it's best to run `make roles` to update the roles downloaded from other sources.
+**From now on**, every time you update the playbook (well, every time the `requirements.yml` file changes), it's best to run `make roles` to update the roles downloaded from other sources. `make roles` is a shortcut (a `roles` target defined in [`Makefile`](Makefile) and executed by the [`make`](https://www.gnu.org/software/make/) utility) which ultimately runs [ansible-galaxy](https://docs.ansible.com/ansible/latest/cli/ansible-galaxy.html) to download Ansible roles. If you don't have `make`, you can also manually run the commands seen in the `Makefile`.
 
 
 # 2022-10-14

docs/installing.md

@@ -2,7 +2,7 @@
 
 If you've [configured your DNS](configuring-dns.md) and have [configured the playbook](configuring-playbook.md), you can start the installation procedure.
 
-**Before installing** and each time you update the playbook in the future, you will need to update the Ansible roles in this playbook by running `make roles`.
+**Before installing** and each time you update the playbook in the future, you will need to update the Ansible roles in this playbook by running `make roles`. `make roles` is a shortcut (a `roles` target defined in [`Makefile`](Makefile) and executed by the [`make`](https://www.gnu.org/software/make/) utility) which ultimately runs [ansible-galaxy](https://docs.ansible.com/ansible/latest/cli/ansible-galaxy.html) to download Ansible roles. If you don't have `make`, you can also manually run the commands seen in the `Makefile`.
 
 
 ## Playbook tags introduction

docs/prerequisites.md

@@ -22,6 +22,8 @@ If your distro runs within an [LXC container](https://linuxcontainers.org/), you
 
 - [`git`](https://git-scm.com/) is the recommended way to download the playbook to your computer. `git` may also be required on the server if you will be [self-building](self-building.md) components.
 
+- [`make`](https://www.gnu.org/software/make/) for running `make roles`, etc. (see [`Makefile`](../Makefile)), although you can also run these commands manually (without `make`)
+
 - An HTTPS-capable web server at the base domain name (`<your-domain>`) which is capable of serving static files. Unless you decide to [Serve the base domain from the Matrix server](configuring-playbook-base-domain-serving.md) or alternatively, to use DNS SRV records for [Server Delegation](howto-server-delegation.md).
 
 - Properly configured DNS records for `<your-domain>` (details in [Configuring DNS](configuring-dns.md)).