Summary:
Added explicit configuration for dependabot. We already use it to be
alerted when CVEs are reported but don't use PRs created by dependabot to
mitigate at the moment.

Test Plan: N/A Just some tooling configs

Reviewers: michelle, zasgar

Reviewed By: zasgar
Signed-off-by: Vihang Mehta <vihang@pixielabs.ai>

Differential Revision: https://phab.corp.pixielabs.ai/D11378

GitOrigin-RevId: c86d8c21dee23fe1fe628817cd4007bef1a9084f