Add slack reporting

[delucchi-cmu]

• I have already created a slack app that will accept incoming messages via the webhook.
• Added webhook URL as a repo secret on this repo.

[github-actions]

Before [712947b]	After [f3fda34]	Ratio	Benchmark (Parameter)
1.73±0.6s	2.79±1s	~1.62	benchmarks.time_computation
3.72k	3.14k	0.84	benchmarks.mem_list

Click here to view all benchmarks.

[camposandro]

@delucchi-cmu, this looks fantastic! Do you have any message sample? I'm curious to see what one of these rich messages looks like!

[delucchi-cmu]

@delucchi-cmu, this looks fantastic! Do you have any message sample? I'm curious to see what one of these rich messages looks like!

This is what it looks like for a RAIL failure from a few weeks ago.

• the weird looking square is an animation caught in the middle
• there's a link to the failed action so you can head straight there
• it's provided as a message that you can reply to or react to, so it's clear who's looking into it or if there was a quick resolution