Directory watch mode

[char101]

The implementation of batch scaling in #21 is useful when resizing several images, but it is difficult to use when the scaling is part of a pipeline. I would like to suggest a directory watch mode. This could simply be a loop where it checks for new files in the input directory for every n-seconds. This way it can shave off the initialization time and can be easily integrated with external script.

[GigaFyde]

could we get this implemented?

[Calinou]

You should be able to use waifu2x-ncnn-vulkan in combination with watchexec already. However, it won't get rid of the initialization time.