Development option to bypass tls checks

[migmartri]

In development, I am running the Harbor Helm chart as target registry to try out this tool.

The issue is that this development instance of Harbor runs with a self signed tls certificate and hence chart-syncer will complain. It might be useful to add a flag that removes that requirement, similar to the one in k8s itself --insecure-skip-tls-verify

Internally that will just add the following to the http client.

	tr := &http.Transport{
		TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
	}
	

PS: I've noticed that we are initializing multiple clients depending on the target/source, we could take this opportunity to initialize the client higher up in the command chain and pass it through the dependent packages.

Thanks!