'filter:retweets` is valid search query but is undocumented

[SaschaNaz]

Combine different search operators for widget search query

Filter out retweets with -filter:retweets Example: puppies -filter:retweets

I think an example for this query should be added on Search API page.

[andypiper]

Thanks for the feedback! We can look at getting that added.

[andypiper]