Added a checkbox to the feature request template for searching for existing requests

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -3,6 +3,13 @@ description: Suggest an idea for Session
 title: '[Feature] <title>'
 labels: [feature-request]
 body:
+  - type: checkboxes
+  attributes:
+    label: Is there an existing request for feature?
+    description: Please search to see if an issue already exists for the feature you are requesting.
+    options:
+    - label: I have searched the existing issues
+      required: true
 - type: textarea
   attributes:
     label: What feature would you like?