docs: Added docs for emergency upgrades

[mmulji-ic]

Description

Closes: #2557

Adds a generic emergency doc, so that all validators understand the process involved with emergency upgrades.

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[greg-szabo]

I'd keep this much briefer for now and only add content that is established for the long term already. I hope that emergency updates are going to look way different by the end of the year, compared to now.

[faddat]

Just wanted to mention that I think this is great!

[alatuszam]

How might one reach the relevant teams at Informal Systems?

Is there an email maintained specifically for security comms cc: @greg-szabo

[faddat]

suggest contacts at:

• informal
• icf
• notional
• amulet

reasoning: one org could be hit by a bus, etc, and this way, we don't have that problem.

We could also have an email that goes to all 4 and document that here. Or, some other solution I didn't think of (basically, encourage this to be multi-organizational)

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[mmulji-ic]

Closing now, as Amulet will provide equivalent documentation for this process.