Created a Github Action that uses the [Review-Bot app](https://github.com/paritytech/review-bot) to require more fine tuned requirements to review pull requests before allowing the PR to be merged.

This uses [`pull_request_target`](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target) for the event, not `pull_request`. This is a security measure so that an attacker doesn’t have access to the secrets.

Added rule which allows the audit team to lock particular important changes when they were created by someone who does not belong to the core-devs team

This resolves paritytech/pr-custom-review#136

Added protection to review bot file which would keep this file from being modified by unknown parties. Added `opstooling` as a required team to ensure that this file does not break

Co-authored-by: Joyce Siqueira <98593770+the-right-joyce@users.noreply.github.com>