revert(core): return settings_value template tag

ref: #824

app/core/templatetags/settings_value.py

@@ -0,0 +1,9 @@
+from django import template
+from django.conf import settings
+
+register = template.Library()
+
+@register.simple_tag
+def settings_value(name):
+
+    return getattr(settings, name, "")