`getBuffer` expects a string, but it could also be a number - if using `AUTO` constant

[olliechick]

The getBuffer function expects a string type for the parameter mime, but a number is actually a valid input - if it is the constant AUTO.

https://github.com/oliver-moran/jimp/blob/7d3fc67abf1bcb4c502a1b404decafb31b2dd0a9/packages/core/src/utils/image-bitmap.js#L195

[olliechick]

I think changing the line to the below would fix it:

 * @param {(string|number)} mime the mime type of the image buffer to be created

[hipstersmoothie]

@olliechick want to submit a PR for that?

[github-actions]

🚀 Issue was released in v0.22.2 🚀

[github-actions]

🚀 Issue was released in v0.22.2 🚀