Add fuzzing by way of ClusterFuzzLite

[DavidKorczynski]

This adds fuzzing by way of ClusterFuzzLite, which is a GitHub action that will perform a short amount of fuzzing for new PRs.

I added a fuzzer that targets the parsing logic, and currently set the timeout of CFLite to 100 seconds. CFLite will flag if the fuzzer finds any issues in the code introduced by a PR.

[mcmtroffaes]

Thanks so much for your contribution! I don't know much about ClusterFuzzLite but it seems quite promising. I want to learn a bit more about it before deciding whether to merge this. The one thing to note here is that this repository rarely gets pull requests, so maybe a monthly (or maybe less) cron would make sense in addition to PR fuzzing. I'm taking a break for the next two weeks but I'll get back to this.

[mcmtroffaes]

... the other thought I had is that likely I'll want to move all testing to github actions - but this is tangential to this pull request.

[DavidKorczynski]

The one thing to note here is that this repository rarely gets pull requests, so maybe a monthly (or maybe less) cron would make sense in addition to PR fuzzing.

We could add this as a follow-up? ClusterFuzzLite supports batch fuzzing which can be controlled by a cron schedule.