docs(newsfragment): add template for significant newsfragments

Closes: apache#44374

newsfragments/template.significant.rst

@@ -0,0 +1,19 @@
+.. Write a short and imperative summary of this changes
+
+.. Provide additional contextual information
+
+.. Check the type of change that applies to this change
+
+* Types of change
+
+  * [ ] DAG changes
+  * [ ] Config changes
+  * [ ] API changes
+  * [ ] CLI changes
+  * [ ] Behaviour changes
+  * [ ] Plugin changes
+  * [ ] Dependency change
+
+.. List the migration rules needed for this change (see https://github.com/apache/airflow/issues/41641)
+
+* Migrations rules needed