A proposal to add code owners for each template

https://blog.github.com/2017-07-06-introducing-code-owners/

How about adding the author of each template to be the code owner? For example,
```
...
bosh-setup/* @bingosummer
...
```
Then code owners will automatically be requested for review whenever a pull request touches the files they own.
I think, it can help maintain the template and avoid unexpected changes.

Start with the linked GitHub Code Owners article and inspect how template paths such as bosh-setup/* are organized in this repository. Determine whether assigning each template author as an owner is feasible across the templates, and consider the result complete when pull requests touching a template can request its listed owner for review.

Written by the indexing model from the issue text.