Feature request: configurable output dir

[sibbl]

I'd like to put my image files into a subdirectory but this doesn't seem to be possible at the time.

I'd expect to be able to pass options like

imageFiles({
   dir: "./assets"
})

which would then be appended using path.resolve to the path which is currently used/extracted from the rollup config.

Is there anything which would speak against it or would a PR be appreciated?

[bspaulding]

PRs welcome, @sibbl!

[dongyuwei]

My fork https://github.com/dongyuwei/rollup-plugin-images implemented this feature. And to resolve the potential name conflict, all images are copied with MD5 hash as part of the file name.