chore: add auto assign app config file.

.github/auto_assign.yml

+# Set to true to add reviewers to pull requests
+addReviewers: true
+
+# Set to true to add assignees to pull requests
+addAssignees: true
+
+# A list of reviewers to be added to pull requests (GitHub user name)
+reviewers:
+  - ruibaby
+  - JohnNiang
+  - guqing
+  - LIlGG
+
+# A list of keywords to be skipped the process that add reviewers if pull requests include it
+skipKeywords:
+  - wip
+
+# A number of reviewers added to the pull request
+# Set 0 to add all the reviewers (default: 0)
+numberOfReviewers: 0
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