.github: add dependabot

[lichunzhu]

What problem does this PR solve?

add dependabot

What is changed and how it works?

add dependabot

Check List

Tests

• Unit test
• Integration test

Release note

• No release note

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[ti-chi-bot]

[FORMAT CHECKER NOTIFICATION]

Notice: To remove the do-not-merge/needs-linked-issue label, please provide the linked issue number on one line in the PR body, for example: Issue Number: close #123 or Issue Number: ref #456.

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