app: add description for memory

dashboard/src/views/app.html

@@ -995,6 +995,7 @@
             <form role="form" name="resourcesForm" ng-submit="resources.submitMemoryLimit()" autocomplete="off">
               <div class="form-group">
                 <label class="control-label" for="memoryLimit">{{ 'app.resources.memory.title' | tr }} <sup><a ng-href="https://docs.cloudron.io/apps/#memory-limit" class="help" target="_blank"><i class="fa fa-question-circle"></i></a></sup> : <b>{{ resources.memoryLimit | prettyBinarySize:'Default (256 MiB)' }}</b></label>
+                <p>{{ 'app.resources.memory.description' | tr }}</p>
                 <input type="range" id="memoryLimit" ng-model="resources.memoryLimit" step="134217728" min="{{ resources.memoryTicks[0] }}" max="{{ resources.memoryTicks[resources.memoryTicks.length-1] }}" list="memoryLimitTicks" />
                 <datalist id="memoryLimitTicks">
                   <option ng-repeat="limit in resources.memoryTicks" value="{{ limit }}"></option>