contribution, license and readme!

CONTRIBUTION.md

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+# Contribution guidelines
+
+## Framework and code
+We use the JUCE Framework, so if you are not familiar with it, please visit their [homepage](https://www.juce.com/). 
+
+For the GUI, it is important to add everything via the Introjucer which you can find in the repository. Everything that is not added via the Introjucer, will be probably removed. 
+
+If you want to add files, you will need as well to add them via the Introjucer - don't forget to add them to the repository as well! 
+
+For the audio, it is important to know that we have a global parameters file. So please look carefully when you want to add a parameter. 
+
+## Pull requests
+
+We are going to try to look into your request as fast as possible, and if it goes through our code review, we will merge it. 
+