message: docs: Update heading styles
diff: ## Motivation
  -This project was created 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). The official predecessor was also deprecated on [July, 19th 2016](https://github.com/coinbase/coinbase-exchange-node/commit/b8347efdb4e2589367c1395b646d283c9c391681).
  +This project was created 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). The official predecessor was also deprecated on [July, 19th 2016](https://github.com/coinbase/coinbase-exchange-node/commit/b8347efdb4e2589367c1395b646d283c9c391681).
  ## Features
  @@ -18,11 +18,13 @@ Advantages over the [official counterpart][3]:
  ## Installation
  +**npm**
  +
  ```bash
  npm install coinbase-pro-node
  ```
  -or:
  +**Yarn**
  ```bash
  yarn add coinbase-pro-node
  @@ -82,7 +84,7 @@ Contributions, issues and feature requests are welcome!
  Feel free to check [issues page](https://github.com/bennyn/coinbase-pro-node/issues).
  -**Maintainers**
  +## Maintainers
  [![Benny Neugebauer on Stack Exchange][stack_exchange_bennyn_badge]][stack_exchange_bennyn_url]
  