Support local images with custom image name

[nishkrishnan]

Hi, when i run:

ko build --local .

I want the ability to have it be published to my local docker daemon with a custom image name instead of ko.local. This allows me to handle pushing to external repositories myself such as when i need to push to multiple. If there's support for this, I can add it.

[nishkrishnan]

As a workaround I usually end up retagging the image using docker and then proceeding with my business.