message: docs: Link to coinbase-pro-node deprecation notice
diff: ## Motivation
  -The purpose of [coinbase-pro-node][5] is to continue an active **Coinbase Pro API** after Coinbase deprecated the official Node.js library on [January, 16 2020](https://github.com/coinbase/coinbase-node/issues/140#issuecomment-574990136). Its predecessor got deprecated on [July, 19th 2016](https://github.com/coinbase/coinbase-exchange-node/commit/b8347efdb4e2589367c1395b646d283c9c391681).
  +The purpose of [coinbase-pro-node][5] is to continue an active **Coinbase Pro API** after Coinbase deprecated the official Node.js library on [January, 16 2020](https://github.com/coinbase/coinbase-pro-node/issues/393#issuecomment-574993096). Its predecessor got deprecated on [July, 19th 2016](https://github.com/coinbase/coinbase-exchange-node/commit/b8347efdb4e2589367c1395b646d283c9c391681).
  ## Features
  