doc: add the start of the CONTRIBUTING document

SlavaVedernikov#100

CONTRIBUTING.md

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+# Contributing to C4InterFlow
+
+## As a Developer
+
+C4InterFlow is developed on dotnet core, and so far development has been done on a Windows machine with Visual Studio.
+Editor files have been put in place to enforce consistency where applicable.
+
+### Environment Prerequisites
+
+* Windows environment
+  * All testing scripts are currently utilizing Windows Batch files.
+* Visual Studio (able to support dotnet 6 or later)
+* Java JRE
+  * Necessary to execute the `plantuml.jar` file to render diagrams
+
+## As a tester
+
+## All Others