Add contribution guide

CONTRIBUTING.md

+# Contributing to SimCAQ API
+
+## Before you get started
+
+### Code of Conduct
+
+By participating of this project you are expected to hold the [Code of Conduct](https://gitlab.c3sl.ufpr.br/simcaq/simcaq-node/blob/development/CODE_OF_CONDUCT.md).
+
+## How Can I Contribute?
+
+### Reporting Bugs
+Bugs are reported and tracked at simcaq/SCRUM repository. As you determinate which repository your bug is related to, create an issue and label it with the appropriate tags.
+
+## Branch structure
+
+* **master**: protected branch and contains the stable version
+* **development**: default branch
+* **issue/??**: issue branch - a branch created to solve a issue
+* **feature_????**: feature branch - a branch created to add a feature
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