ci: create gemini code reviewer configuration

(cherry picked from commit 2b484da)

Author: josephperrott

.gemini/config.yaml

@@ -0,0 +1,11 @@
+have_fun: false
+code_review:
+  disable: false
+  comment_severity_threshold: MEDIUM
+  max_review_comments: -1
+  pull_request_opened:
+    help: false
+    summary: false
+    code_review: true
+    include_drafts: false
+ignore_patterns: []