20210420 bugfree

The bug-free software guarantee.

1. Find a bug, get a free licence
2. If you already have a licence, get the next one free (incentive to find bugs in the 2-4 week trial period)
3. What if everyone finds a bug, and everyone gets a free licence? That's OK. If nobody is able to use Ragdoll without finding a bug, Ragdoll does not deserve payment.

Requirements:

1. Bug must be reproducible in the latest version
2. Bug must not already have been reported, first-come first-served (tracked via GitHub issues)
3. But must not already be known (tracked via GitHub)