add(contributing): creates contributing guide

Author: andre-filho

CONTRIBUTING.md

@@ -0,0 +1,21 @@
+# Contributing to the project
+
+## Greetings
+
+First and foremost, we appreciate your contribution in this project. :)
+
+**Welcome to our community!**
+
+## How can I help?
+
+You can start contributing to this project by:
+
+- Closing issues
+- Opening issues and reporting bugs
+- Proposing new features
+- Helping in code quality and maintenance
+
+## What do I need to know before getting started?
+
+Actually, you need to read only our [README](README.md), our [CODE OF CONDUCT](CODE_OF_CONDUCT.md) and know that we have pull request and issue templates, so they are to be followed.
+