Merge #964

964: Create overrides/nginx r=mergify[bot] a=jeremyVignelles

## What type of PR?

documentation

## What does this PR do?
Updates the procedure to include the creation of that required folder

## Prerequistes
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [X] In case of feature or enhancement: documentation updated accordingly
- [X] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.


Co-authored-by: Jérémy VIGNELLES <jeremyvignelles@users.noreply.github.com>

setup/flavors/stack/setup.html

@@ -4,7 +4,7 @@
 <p>Docker Stack expects a project file, named <code>docker-compose.yml</code>
 in a project directory. First create your project directory.</p>
 
-<pre><code>mkdir -p /{{ root }}/{redis,certs,data,dkim,mail,overrides/rspamd,filter,dav,webmail}
+<pre><code>mkdir -p /{{ root }}/{redis,certs,data,dkim,mail,overrides/rspamd,overrides/nginx,filter,dav,webmail}
 </pre></code>
 
 <p>Then download the project file. A side configuration file makes it easier