Add hard-coded breadcrumbs to documentation files about installation procedure for easier navigation (#3745)

* Add hard-coded breadcrumbs to documentation files about installation procedure for easier navigation

Since it is easy to get lost among these files, the breadcrumbs should be helpful to get the whole picture of the procedure. Hopefully they will be replaced with something else generated automatically.

Please note that the usage of <sup> HTML tags on this context is not proper as the tag is intended to be used only for typographical reasons. Here <small> tags should rather be used instead as long as we do not use CSS, but since GitHub strips these tags against its spec (https://github.github.com/gfm/#disallowed-raw-html-extension-) (also note: the <small> HTML tags are not stripped on Codeberg for example), this commit intentionally uses <sup> to have those breadcrumbs rendered in small points.

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

* Update docs/configuring-playbook.md title

The file is referred from other files as "Configuring the playbook"

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

* Add "Quick start" link with the thunder icon

For now docs/README.md is linked

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

---------

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

docs/prerequisites.md

@@ -1,5 +1,7 @@
 # Prerequisites
 
+<sup>⚡️[Quick start](README.md) | Prerequisites > [Configuring your DNS server](configuring-dns.md) > [Getting the playbook](getting-the-playbook.md) > [Configuring the playbook](configuring-playbook.md) > [Installing](installing.md) </sup>
+
 To install Matrix services using this Ansible playbook, you need:
 
 - (Recommended) An **x86** server ([What kind of server specs do I need?](faq.md#what-kind-of-server-specs-do-i-need)) running one of these operating systems that make use of [systemd](https://systemd.io/):