Prompt bug reporters to test NIGHTLY (#930)

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -46,6 +46,18 @@ body:
     validations:
       required: true
 
+  - type: dropdown
+    id: nightly-repro
+    attributes:
+      label: Can you reproduce this on cmux NIGHTLY?
+      description: "Please test with the latest NIGHTLY build first: https://github.com/manaflow-ai/cmux?tab=readme-ov-file#nightly-builds"
+      options:
+        - Yes, it still reproduces on NIGHTLY
+        - No, it does not reproduce on NIGHTLY
+        - I could not test NIGHTLY
+    validations:
+      required: true
+
   - type: textarea
     id: description
     attributes: