Project Overview Documentation [Request for Comment]

This is a draft of documentation for people who visit the project page on Github to understand what the project is.
As well as provide information for new developers on how to contribute to the project.

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### documentation
* **README.md**: this is the first document people will see when visiting the repository. It contains a one sentence to one paragraph long description of the project. As well as instructions on how to install and run the project.
* **CONTRIBUTING.md**: this is a set of instructions for how developers can contribute to the project and the guidelines they should follow to do so.
* **DESIGN.md**: this document covers the key concepts of the project, and an architectural overview of how it is designed.

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the documents can be viewed on github by visiting https://github.com/IMOD-ASU/imod/pull/86/files
and clicking on ```view``` in the top right corner of each diff.
comments can be left on a specific line from the diff view or be left on the conversation page https://github.com/IMOD-ASU/imod/pull/86.