bumping sharp version to 0.28.3 to support arm64 on macOS

[benjibee]

Fixes #150 by upgrading sharp to a version that support arm64 on macOS

[wszydlak]

This also fixes #149

[benjibee]

That makes sense but I'm not enough into this project at the moment to write those tests.

I'm currently using it to create webp, png, and jpeg images in various sizes with renaming, etc. and it's so far without any errors though I understand that's not the same as test coverage ;)

[dutscher]

i have problems with node14. can we please push forward the upgrade to 0.28.3?

cheers

[ingomc]

i also want it to use with node >= 14