Create incident handbook entry

[timgl]

Changes

Our response to an incident today was okay, but there were a few areas for improvement:

• There were a couple of separate threads with different people solving the same problem
• we didn't communicate well to customers
• We didn't take any good notes until the very end
• We're not sure whether it was actually resolved

I propose we use incident.io to respond to incidents. This will

• Automatically create a channel for new incidents with a zoom link so everyone knows where to look. It'll also post that an incident is ongoing in #incidents, so the rest of the company knows what's going on
• It'll provide us with a better log of what happened
• It'll help us with incident analysis afterwards.

In the future:

• we'll be able to automatically update our status page (might need to move back to statuspage.io)
• we'll be able to have a feed of incidents in posthoguser slack (they don't support this out of the box, but perhaps zapier)
• We might even be able to have a feed directly in our product (api?)

Checklist

• [ ] Titles are in sentence case
• [ ] Feature names are in title case
• [ ] Words are spelled using American English
• [ ] I have checked out our style guide

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[charlescook-ph]

@timgl still looking to merge this PR?

[timgl]

@fuziontech suggested we just use pagerduty instead of incident.io, but haven't had a change to look at that

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[ellie]

👋 @guidoiaquinti @yakkomajuri

I've made some adjustments as ik Tim doesn't have the bandwidth to push this through atm. As you both reviewed this before, mind giving it a once over? I'd like to get this merged asap if possible.

Thanks!