add rounded edges modifier

[tasiotas]

Describe the feature

Could you please add rounded edges modifier so we can specify radius and output rounded/circular images?

Found few examples of implementation in Sharp, unfortunately its beyond me to contribute this feature.

https://github.com/lovell/sharp#stream
lovell/sharp#2268 (comment)
lovell/sharp#3467 (comment)

thank you

Additional information

• Would you be willing to help implement this feature?

[DesertCookie]

I would love to se this added too. It'd be a lot easier than messing around with HTML rounded corners for images that have object-fit: container.