Change the widget used by the navbar element description

ref issue #1

navbar/admin.py

@@ -1,9 +1,20 @@
 from django.contrib import admin
+from django import forms
 from .models import Element, ElementDescription, ElementSeparator
 
 
+class ElementDescriptionAdminForm(forms.ModelForm):
+    class Meta:
+        model = ElementDescription
+        widgets = {
+            'description': forms.widgets.Textarea,
+        }
+        fields = '__all__'
+
+
 class ElementDescriptionInline(admin.StackedInline):
     model = ElementDescription
+    form = ElementDescriptionAdminForm
     extra = 2