Add missing example for minimum viable FluidMail Template (#5208)

* Missing Example for Template

* Move anchor above its headline

* Use directory tree and insert a headline for the example

---------

Co-authored-by: Lina Wolf <[email protected]>

Author: in-session

Documentation/ApiOverview/Mail/Index.rst

@@ -70,10 +70,47 @@ If you want to provide custom templates or layouts, set this in your
     :caption: config/system/additional.php | typo3conf/system/additional.php
 
     $GLOBALS['TYPO3_CONF_VARS']['MAIL']['templateRootPaths'][700]
-        = 'EXT:my_site_extension/Resources/Private/Templates/Email';
+        = 'EXT:my_site_package/Resources/Private/Templates/Email';
     $GLOBALS['TYPO3_CONF_VARS']['MAIL']['layoutRootPaths'][700]
         = 'EXT:my_site_extension/Resources/Private/Layouts';
 
+..  _mail-configuration-fluid-example:
+
+Minimal example for a Fluid-based email template
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+**Directory Structure:**
+
+..  directory-tree::
+    :show-file-icons: true
+
+    *  EXT:my_site_package/
+
+        *   Resources
+
+            *   Private
+
+                *   Templates
+
+                    *   Email
+
+                        *   MyCustomEmail.html
+
+**`MyCustomEmail.html`:**
+
+..  code-block:: html
+    :caption: EXT:my_site_package/Resources/Private/Templates/Email/MyCustomEmail.html
+
+    <f:layout name="SystemEmail" />
+
+    <f:section name="Subject">
+        My Custom Subject
+    </f:section>
+
+    <f:section name="Main">
+        Hello, this is a custom email template!
+    </f:section>
+
 ..  _mail-configuration-transport:
 
 transport