Contribution guidelines and template

CONTRIBUTING.md

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+## Contributing
+
+You can cntribute to **30 seconds of code** by sending pull requests for snippets that you find useful, reporting issues with current snippets or suggesting changes and/or additions.
+
+### Guidelines for new snippets
+
+- Snippets must be short. Usually anything above 10 lines would be considered too long, but you can still submit it as it might be possible to shorten it or it might still prove useful regardless of its length.
+- Snippets must be explain to a certain extent in the description above them. Make sure to include what functions you are using and why.
+- Snippets must solve real-world problems and should be abstract enough to use in different scenarios. This is highly subjective, so send them in anyways.
+- Snippets *should* be written in ES6 if possible.
+- Snippet files must follow the anchor name conventions of (GitHub Flavored Markdown)[https://github.github.com/gfm/], so that the `builder.js` can build the links for the list.
+- Use the [template](snippet-template.md) to format your snippets.
+- If possible, provide test cases in your Pull Request (link or comment), so that it's easier to verify that each snippet is working. 

snippet-template.md

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+### Snippet title
+
+Explain briefly how the snippet works
+
+```js
+var functionName = arguments => 
+  {functionBody}
+```