app.rerun.io includes a nice examples page now, so we don't need demo.rerun.io anymore.

We still have to build the .rrd files somewhere.

Many places have hardcoded paths to demo.rerun.io, we should be careful about replacing those.

We should redirect demo.rerun.io to app.rerun.io.

demo.rerun.io is currently our best way to browse live examples, but we can solve this by linking to individual examples (on app.rerun.io) from Link to app.rerun.io from https://www.rerun.io/examples/real-data/