fuzz action

[gilescope]

Motivation

How much fuzzing is the right amount? Idk, but given that you can't have too much of a good thing maybe we should have a little fuzzing with each commit. (I'm assuming it will start at a different seed each time). If it finds anything then we can add it to the standard test suite.

Workflow example

cargo fuzz run fuzz_me -- -max_total_time=20s

Thoughts? Thumbs up / down?

Advatages

If there's a real clanger of a bug that we've just introduced then a little fuzzing might well pick it up straight away.
And over time it might find those long tail bugs.

Disadvantages

Chews threw a bit of CI minutes.

[gilescope]

Happy to provide a PR if you are ok with the idea.