set-interval/CONTRIBUTING.md

start and clear interval without setting a variable

# Contributing

✨ Thank you for contributing ✨

There are just guideliness.

Please feel free to contribute by submitting PR's for improvements to code snippets, explanations, etc.

## Submitting an issue

Found a problem? Have an enhancement? 

First of all see if your issue or idea has already been [reported](https://github.com/shystruk/SetIntervalJS/issues).

If do not, open a [new one](https://github.com/shystruk/SetIntervalJS/issues/new).

## Submitting a pull request

- Fork this repository
- Clone fork `git clone ...`
- Navigate to the cloned directory
- Install all dependencies `npm install`
- Crate a new branch for the feature `git checkout -b new-feature`
- Make changes
- Run tests `npm run test`
- Commit changes `git commit -am 'What is feature about? :)'`
- Push to the branch `git push origin new-feature`
- Submit a PR