chore: contrib guideline before opening a pr (#338)

Author: Gui ⚡️ Guilherme Ferreira

CONTRIBUTING.md

@@ -6,6 +6,14 @@ Please note that this project is released with a [Contributor Code of Conduct][c
 
 ## Submitting a pull request
 
+### Before opening a Pull Request
+
+We recommend [opening an issue](https://github.com/Farfetch/kafkaflow/issues) before a substantial Pull Request if there isn’t [already an issue](https://github.com/Farfetch/kafkaflow/issues) for what you’d like to contribute. This helps facilitate a discussion before deciding on an implementation approach.
+
+For some changes, such as typo fixes, documentation enhancements, or broken links, it may be suitable to open a small Pull Request by itself.
+
+### How to open a Pull Request
+
 1.  Check the issues or open a new one
 2.  Fork this repository
 3.  Create your feature branch: `git checkout -b my-new-feature`
@@ -33,7 +41,6 @@ Run command `make init_broker`
 
 Run command `make shutdown_broker`
 
-
 ## Resources
 
 -   [How to Contribute to Open Source](https://opensource.guide/how-to-contribute/)
@@ -44,4 +51,4 @@ Run command `make shutdown_broker`
 
 By sending us your contributions, you are agreeing that your contribution is made subject to the terms of our [Contributor Ownership Statement](https://github.com/Farfetch/.github/blob/master/COS.md)
 
-[code-of-conduct]: CODE_OF_CONDUCT.md
+[code-of-conduct]: CODE_OF_CONDUCT.md