ci: add a github action to send slack notification if number of reactions exceeds threshold in PRs and issues

[pragya-20]

Description

• This is a GitHub action that will count the number of reactions to an issue or a PR. If the total count exceeds the threshold reactions, it will send a slack notification notifying the user.
• The threshold reaction is defined in the environment variable as THRESHOLD_REACTIONS
• To receive the slack notification, one may create a slack app and provide the token as a secret named SLACK_BOT_TOKEN
• This action will run daily at 8:00 am (GST) as people start their day around the similar time
• It will also be triggered once anyone comments on an issue or PR

Related issue(s) Resolves #41

[derberg]

Thanks but I need to close this PR. There is already a draft PR @14Richa is working on https://github.com/asyncapi/.github/pull/220 and I've already provided lots of feedback there