Use HTML version of incident message in atom feed

Atom (not RSS) feeds are able to handle html in entry content, so it
makes sense to put HTML version of incident in it.

app/Http/Controllers/AtomController.php

@@ -16,6 +16,7 @@ use CachetHQ\Cachet\Models\ComponentGroup;
 use CachetHQ\Cachet\Models\Incident;
 use Illuminate\Support\Str;
 use Roumen\Feed\Facades\Feed;
+use GrahamCampbell\Markdown\Facades\Markdown;
 
 class AtomController extends AbstractController
 {
@@ -65,7 +66,7 @@ class AtomController extends AbstractController
             Setting::get('app_name'),
             Str::canonicalize(Setting::get('app_domain')).'#'.$incident->id,
             $incident->created_at->toAtomString(),
-            $incident->message
+            Markdown::convertToHtml($incident->message)
         );
     }
 }