Create CONTRIBUTING.md

Author: davetcc

CONTRIBUTING.md

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+## Summary
+
+First of all let me say that we are very glad to have any contributions to the library; as the more people developing and
+looking over and testing it, the more likely it is to be stable and succeed. I'm not one for liking hard and fast rules,
+but like any community a few rules are needed in order to ensure things go smoothly.
+
+* Don't start working on any large features without creating an issue first, this allows for feedback before proceeding, 
+  potentially avoiding a lot of wasted time later.
+* Please try and use a similar code style to the rest of the project. At an absolute minimum please keep fields,
+  variable styles and braces the same. Use camel case for all variables. Functions should always start with a lower
+  case letter. Classes always start with an upper case letter.
+* Please be sure that you're happy with the licensing model of this project. For any files you create, you can retain
+  copyright, but they must be provided under the same Apache as the rest of the project, and with copyright granted to
+  the library at the top of the file.
+* If you edit keywords.txt, be exceptionally careful that tabs have not been replaced as spaces.
+* If using Arduino: Please make sure that compiler warnings are set to All, (Arduino Menu -> Preferences -> Compiler warnings)
+* If using platformIO (recommended): See [https://github.com/davetcc/tcLibraryDev]
+  
+## Why do all TheCodersCorner libraries use an Apache license?
+
+The apache license allows others to use this library commercially. You may ask why that is important, it is important
+because any strong and stable ecosystem, such as Java, has got where it is because it's used by the Hobbyist, the
+Enterprise, start-ups and just about any other group you care to mention.
+
+I think it's a shame that so many Arduino libraries are GPL instead of Apache, LGPL or MIT; as it means these can't be used
+by commerical entities, at least without contacting the vendor of the library first. Will they bother to do that, NO, they
+will just write what they need to get the job done and probably never give it back. If the library were open, and this
+same commerical made changes, they could well decide to give them back!