Support the `jxl` format

[atjn]

Hi :)

It would be really nice if mrmime could support the Jpeg XL (jxl) format. The Vite project is currently implementing a workaround because it is not available in mrmime: vitejs/vite#18855

The file format is already supported in mime-db so I think you just need to release a new version with updated data to support this format.