Add favicon that's related to Kustomize

[bugoverdose]

This should be a sub-task of https://github.com/kubernetes-sigs/kustomize/issues/5290.

Currently we are using default favicons in the docsy submodule, which is not related to Kustomize.

Replace the favicons with something related to kustomize or k8s.

cc. @annasong20

[natasha41575]

/kind documentation /triage accepted

[sarab97]

@natasha41575 i guess this can be closed now. I see favicon is now added.

[natasha41575]

@sarab97 Sorry, I can't seem to find the PR that adds the favicon? If you are looking at kustomize.io, that is the site that we are trying to replace and is unrelated to the site directory that is sitting in this repo.

[loffing]

/assign

[loffing]

/unassign

[jakezhu9]

/assign