Updated models.py

Added announcement branch's models.py file

widget_group3/widget_group3/models.py

 from django.db import models
-from django.urls import reverse
\ No newline at end of file
+from django.urls import reverse
+
+class Announcement(models.Model):
+    announcement_title= models.CharField(max_length=50)
+    announcement_body = models.CharField(max_length=200)
+    pub_date = models.DateTimeField(auto_now_add=True)
+
+    def __str__(self):
+        return self.announcement_title
\ No newline at end of file