ci: Add blunderbuss config (#77)

Co-authored-by: Averi Kitsch <akitsch@google.com>

Author: duwenxin99

.github/blunderbuss.yml

@@ -0,0 +1,4 @@
+assign_issues:
+  - googleapis/langchain-csql-mysql
+assign_prs:
+  - googleapis/langchain-csql-mysql

.github/header-checker-lint.yml

@@ -11,6 +11,7 @@ sourceFileExtensions:
   - "py"
   - "text"
 ignoreFiles:
+  - ".github/blunderbuss.yml"
   - ".github/release-please.yml"
   - ".github/release-trigger.yml"
   - ".github/header-checker-lint.yml"