bug #3545 Show panel icon in detail view (lukasluecke)

This PR was merged into the 3.0.x-dev branch.

Discussion
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Show panel icon in detail view

Fixes #3544

<img width="394" alt="CleanShot 2020-07-13 at 17 51 19@2x" src="https://user-images.githubusercontent.com/6652670/87325232-7a0d9000-c531-11ea-8572-e3c353e21384.png">

Commits
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325fcba Show panel icon in detail view

src/Resources/views/crud/detail.html.twig

@@ -100,6 +100,9 @@
     <div class="{{ field.cssClass }}">
         <div class="content-panel">
             <div class="content-panel-header">
+                {% if field.customOption('icon') %}
+                    <i class="{{ field.customOption('icon') }}"></i>
+                {% endif %}
                 {{ field.label|raw }}
 
                 {% if field.help is not empty %}