Add issue labels to the email body

The Kubernetes team wants to route issues emails based on labels.

Can we include the labels at the bottom of each issue email, maybe like:

Labels: [Submodule X] [Submodule Z] [UX]

We talked about adding it to the subject line but one issue might have many labels.

I think this easy to do and we should support it.

What do @JobV and @dzaporozhets think?