Feat: ephemeralContainer support (kubectl debug)

I just wanted to check if you guys were amenable to a PR to cover adding support for kubectl debug on pods?

I have something pretty much ready but my registry at home is using my own CA cert so I need to do a little patching to allow the crane libraries to be able to trust it for final testing.

We just find it a bit annoying having to go an check a sha for a tagged version when we debug and digester otherwise does a great job in other cases to obviate the need to do this with our binary auth setup on GKE.

Also, this is a silent feature at present, do you prefer a flag to turn on the setting or should it just be enabled by default and work? This also brings up any documentation requirements you might think appropriate, obviously with a flag to enable there will need to be document updates.

The user of course will have the option to disable it should they wish by removing a line in the mutatingwebhookconfiguration so that's maybe worth documenting.