Add bash completion cmd

Makefile

cmd/tk/completion.go

cmd/tk/delete_kustomization.go

cmd/tk/delete_source_git.go

docs/cmd/tk.md

docs/cmd/tk_check.md

docs/cmd/tk_completion.md

docs/cmd/tk_create.md

docs/cmd/tk_create_kustomization.md

docs/cmd/tk_create_source.md

docs/cmd/tk_create_source_git.md

docs/cmd/tk_delete.md

docs/cmd/tk_delete_kustomization.md

docs/cmd/tk_delete_source.md

docs/cmd/tk_delete_source_git.md

docs/cmd/tk_export.md

docs/cmd/tk_export_kustomization.md

docs/cmd/tk_export_source.md

docs/cmd/tk_export_source_git.md

docs/cmd/tk_get.md