add contributing guide

contributing.md

@@ -0,0 +1,55 @@
+# Contributing to Portainer Documentation
+
+We want to create a unique place to have all the documentation of Portainer, for the past releases and future ones. This documentation will be hosted in this address (In definition).
+
+## Make suggested updates
+
+### Fork and clone Portainer Documentation Repository
+[Fork this repository](https://help.github.com/articles/fork-a-repo/) and [clone it](https://help.github.com/articles/cloning-a-repository/) to your local machine.
+
+### Run the documentation locally (optional)
+To run the documentation locally, follow the instructions provided in the [README](readme.md).
+
+### Make your changes
+Make your suggested changes being sure to follow the [style and formatting guidelines](#style--formatting) outline below.
+
+### Submit a pull request
+Push your changes up to your forked repository, then [create a new pull request](https://help.github.com/articles/creating-a-pull-request/).
+
+## Style & Formatting
+
+### Markdown
+All of our documentation is written in [Markdown](https://en.wikipedia.org/wiki/Markdown).
+
+### Semantic Linefeeds
+Use [semantic linefeeds](http://rhodesmill.org/brandon/2012/one-sentence-per-line/).
+Separating each sentence with a new line makes it easy to parse diffs with the human eye.
+
+**Diff without semantic linefeeds:**
+``` diff
+-Kubernetes is taking off. You need a cool management tool to manage it. You should check out Portainer.
++Kubernetes is taking off. You need a cool management tool to manage it. You need Portainer.
+```
+
+**Diff with semantic linefeeds:**
+``` diff
+Kubernetes is taking off.
+You need a cool management tool to manage it.
+-You should check out Portainer.
++You need Portainer.
+```
+
+### Details
+We want to build a reliable Admin guide for each version of Portainer. It's essential to explain the details about that configuration/installation or troubleshooting guide. We don't want an easy and simplified guide or tutorial. Don't use acronyms, but if you're using, please, create a link to an explanation about those.
+
+### Screenshots
+
+Screenshots are welcome. Make sure that you're using the version of Portainer of the documentation you're writing. If you're contributing to Portainer CE v2.0, use an instance of Portainer CE 2.0 to take screenshots.
+
+### Doubts and questions.
+
+We're thankful for your contributions; if you have any doubt, please, open an issue to address that doubt or question.
+
+### Something to contribute for this guide?
+
+All contributions are thankfully and welcome. If you see improvements to do to this guide, please, create a pull request with the details.