Add host_talent and contributors fields to credits trait

[edziegle]

5 years ago, a proposal was accepted to add host_talent and contributors to the credits trait for video content. However, this was never formally implemented. This PR intends to finally correct that.

[edziegle]

See #191

[calexicoz]

Howdy.

This looks ok, but every change to the ANS schema requires changing the ANS version. Can you do this:

https://github.com/washingtonpost/ans-schema#creating-a-new-ans-version

Once the new version has been created, there is an internal release process to go through to make it available to use.

Thanks!

[edziegle]

Howdy.

This looks ok, but every change to the ANS schema requires changing the ANS version. Can you do this:

https://github.com/washingtonpost/ans-schema#creating-a-new-ans-version

Once the new version has been created, there is an internal release process to go through to make it available to use.

Thanks!

Should I go ahead and move this into the current dev version, or just make a 0.10.12?

[calexicoz]

Should I go ahead and move this into the current dev version, or just make a 0.10.12?

This needs to be a new version.