feat(infra): related issues for bug report template (#34913)

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -70,6 +70,16 @@ body:
         - label: langchain-qdrant
         - label: langchain-xai
         - label: Other / not sure / general
+  - type: textarea
+    id: related
+    validations:
+      required: false
+    attributes:
+      label: Related Issues / PRs
+      description: |
+        If this bug is related to any existing issues or pull requests, please link them here.
+      placeholder: |
+        * e.g. #123, #456
   - type: textarea
     id: reproduction
     validations: