Update maintainers and add kpt codeowners
* @GoogleContainerTools/skaffold-team
-# Buildpacks owners
-
-**/**buildpacks** @GoogleContainerTools/skaffold-team
-
# JIB owners
**/**jib** @GoogleContainerTools/skaffold-team @loosebazooka @TadCordle @chanseokoh
+# kpt owners
+pkg/skaffold/deploy/**kpt** @GoogleContainerTools/skaffold-team @yuwenma
+
# Debug owners
pkg/skaffold/debug/** @GoogleContainerTools/skaffold-team @loosebazooka @quoctruong
