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

[kartiklunkad26]

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!

[cppforlife]

i believe the ask is not about any docs (since we do have reference material which counts as a type of docs) but rather guides specifically on how to use this feature (we also do not have guides for other builders either).

[aaronshurley]

Updated the title to reflect the request for a guide since we do have general reference material: https://carvel.dev/kbld/docs/v0.34.0/config/#ko