Local: Add more useful data to DB

[pkevan]

Currently the sample data which we ship with the docker install is minimal (mainly site setup).

We should add the following data to allow easier debugging/setup:

Within Seattle 2023 and Events

• speakers (at least 5)
• attendees (at least 10)
• ticket types (at least 2)
• organizers (at least 5)

There is probably other elements we could easily add, but this would be a good start.