Allow to use a custom slot refresher

[trojanowski]

We're using a yield optimizer which requires us to use a proprietary function for refreshing slot instead of googletag.pubads().refresh() (for header bidding etc.). This PR allows that by specifying the slotRefresher property. googletag.pubads().refresh() is still used as the default one.

[seeden]

@trojanowski are you still using this module? I am updating whole package and I am thinking about adding this feature. I realized that I am using your react-apollo-hooks library :) nice coincidence

[trojanowski]

@trojanowski are you still using this module? I am updating whole package and I am thinking about adding this feature.

Yes, I do. I'm using my custom build right now because I need the feature from this PR. But it would be nice to use the official version from npm again. :)

I realized that I am using your react-apollo-hooks library :) nice coincidence

:)

[csims]

Hi @seeden ! I was wondering if there's still any interest in adding this feature. My team is currently using this library, but need to integrate with Amazon's Transparent Ad Marketplace for header bidding, so we're looking for the ability to use a custom slot refresher function.