Added contributing file to .github folder

.github/contributing.md

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+# Contributing
+
+Great that you want to contribute to the `EthereumJS` [ecosystem](https://ethereumjs.readthedocs.io/en/latest/introduction.html). `EthereumJS` is managed by the Ethereum Foundation and largely driven by the wider community. Everyone is welcome to join the effort and help to improve on the libraries (see our [Code of Conduct](https://ethereumjs.readthedocs.io/en/latest/code_of_conduct.html) 🌷).
+
+We have written up some [Contribution Guidelines](https://ethereumjs.readthedocs.io/en/latest/contributing.html#how-to-start) to help you getting started.
+
+These include information on how we work with **Git** and how our **general workflow** and **technical setup** looks like (stuff like language, tooling, code quality and style).
+
+Happy Coding! 👾 😀 💻