Move our bemo playground from dotcom to the examples app. In preparation
for more multiplayer examples, I built our a little bit of chrome around
example room IDs: if you create an example with `multiplayer: true`, the
examples app will render a little room ID picker above your example. The
room IDs are scoped to each example, and each deploy of the examples
app. By default people on the same example will be in the same room, but
the default ID changes every hour.
As I was doing this, I noticed you could get an ugly situation where the
docs site was in dark mode, tldraw was in dark mode, but the little bit
of examples chrome was in light mode. To fix this I through together an
extremely rough dark mode for the examples which switches on whenever
the tldraw instance inside is in dark mode.
### Change type
- [x] `other`
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Co-authored-by: David Sheldrick <d.j.sheldrick@gmail.com>
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