Project restructure and automated testing

[matthijs166]

I think the project can improve a lot if we restructure some files to make the source code more readable. And add some automated testing into the project for quality insurance

[invakid404]

There's room for improvement here for sure. I've hacked this entire project in a single sitting and I definitely didn't write it with testability in mind :D

Any suggestions and PRs are welcome. I'll think about ways to improve things in the near future as well.

[invakid404]

I've been thinking about this again, I'm thinking of incorporating some integration tests, i.e. spinning up a sample Payload project and running some tests via the API (e.g. uploading an image, verifying that Blurhash is computed). This should also help catch any incompatibilities with new Payload versions that might occur in the future.

Unit testing wouldn't bring much value, as all this plugin does is glue together a few libs, so if anything, I'd be testing that third-party libs behave the way I'd expect them. Integration tests would be pretty useful though, I'll look into arranging that in the near future.