Adding runner UX strategy page

Why is this change being made?

We don't have documentation around runner UX strategy/direction/processes today. I'd like to add that for more visibility and transparency as to what Runner UX is up to, as well as a place for new runner UXers to get acquainted with ongoing work and processes.

There's A LOT that needs to be added so that is why this is marked as a draft for the time being 😃

Author Checklist

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