Add type for Producer.createWriteStream
Add type for Producer.createWriteStream

Update TypeScript type declaration file to include definiton of
Prouder.createWriteStream method.

Fixes: https://github.com/Blizzard/node-rdkafka/issues/724

Blizzard/node-rdkafka,Blizzard/node-rdkafka,Blizzard/node-rdkafka,Blizzard/node-rdkafka