Add support for HostAliases

[lwille]

Description

Our use case requires adding some aliases to /etc/hosts.
Kubernetes allows specifying hostAliases on a Pod like so:

    spec:
      hostAliases:
        - hostnames:
          - example.net
          ip: 127.0.0.1

We've tested this change in our environment and it works well.
It also passes testing with kubeconform:

helm template step-certificates step-certificates --set-json hostAliases='[{"ip":"127.0.0.1", "hostnames":["example.net"]}]' | kubeconform

Please cut a minor release after merging, so we can use it at @wireapp.

❤ Thank you for accepting this humble contribution!

[CLAassistant]

All committers have signed the CLA.

[lwille]

@maraino @hslatman I just resynced our fork, do you have any feedback regarding the change?

[hslatman]

Thank you, @lwille 😄

[lwille]

@hslatman would you mind bumping the chart version and releasing it? I've already published a PR to bump the version: #194

[hslatman]

Have opened #195 instead.

[lwille]

Nice, thank you!