chore: mention security policy in github issue template (#38)

Author: wzxxing

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -8,7 +8,7 @@ body:
   - type: textarea
     id: description
     attributes:
-      label: Describe the bug
+      label: Describe the bug (Security related? please follow <https://github.com/aws/aws-mcp-proxy/security/policy> to report them to AWS Security directly.)
       description: What is the problem? A clear and concise description of the bug.
     validations:
       required: true

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -8,7 +8,7 @@ body:
   - type: textarea
     id: description
     attributes:
-      label: Describe the feature
+      label: Describe the feature (Security related? please follow <https://github.com/aws/aws-mcp-proxy/security/policy> to report them to AWS Security directly.)
       description: A clear and concise description of the feature you are proposing.
     validations:
       required: true

.github/ISSUE_TEMPLATE/questions.yml

@@ -8,7 +8,7 @@ body:
   - type: textarea
     id: question
     attributes:
-      label: Your question
+      label: Your question (Security related? please follow <https://github.com/aws/aws-mcp-proxy/security/policy> to report them to AWS Security directly.)
       description: A clear and concise description of the question.
     validations:
       required: true