[TASK] Setup a script to automatically notify Slack if/when Tangle testnet & mainnet stall

[yurixander]

It should notify Slack when/if the blockchain stops producing/finalizing blocks or taking abnormal times to do so, or other common problems.

One idea for implementation would be via a serverless function, set to run at certain intervals and perform the aforementioned checks, then notify Slack by triggering a web hook and pinging relevant people.

Also take into account a method to prevent spamming the channel with alerts in case it stalls for a long time, have it notify for example max 1 time per 5h or so.