add delete-all in test-data page

judge/views/about.py

@@ -0,0 +1,14 @@
+from django.shortcuts import render
+from django.utils.translation import gettext as _
+
+
+def about(request):
+    return render(request, 'about/about.html', {
+        'title': _('About'),
+    })
+
+
+def custom_checker_sample(request):
+    return render(request, 'about/custom-checker-sample.html', {
+        'title': _('Custom Checker Sample'),
+    })