feat: Users can create Activities

Resolves #22

activities/forms.py

@@ -0,0 +1,14 @@
+from django import forms
+
+from . import models
+
+
+class ActivityForm(forms.ModelForm):
+    class Meta:
+        model = models.Activity
+        fields = [
+            'name',
+            'series',
+            'type',
+            'medium',
+        ]