[Guides] Building images with `KO` and `kbld`

kbld supports building images with `ko` but we don't have any docs on how to use this capability. This story is to write docs corresponding to it!

The issue names no files, tests, or documentation entry point. Start by locating the existing kbld guides and the documented ko integration, then add usage documentation for building images with ko through kbld. Done means the capability has a clear, usable guide.

Written by the indexing model from the issue text.