[CI] add github action requesting review by label

[zetwhite]

Motivation

If I want to get N approvals from @Samsung/one_onert on specific PR, I always have to assign the team N times as reviewers.
It is quite troublesome.

Suggestion

I'd like to add a Github Action that assigns the team as a reviewer based on given labels.
For example, if a PR has labels(approval: 2, review-by/onert), Let's make a github action assign the onert-team until It meets the approval count.

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I don't know if a similar suggestion has been before or not.
So, feel free to give any comments!

[jyoungyun]

I suggest using github-script to control GitHub REST API. :)

github-script:
https://github.com/actions/github-script

How to check the approved count:
https://docs.github.com/en/rest/pulls/reviews?apiVersion=2022-11-28#list-reviews-for-a-pull-request

How to add reviewers:
https://docs.github.com/en/rest/pulls/review-requests?apiVersion=2022-11-28#request-reviewers-for-a-pull-request