docs: added CONTRIBUTING.md (#188)

# Contributing to [github-readme-stats](https://github.com/anuraghazra/github-readme-stats)

We love your input! We want to make contributing to this project as easy and transparent as possible, whether it's:

- Reporting a issue

- Discussing the current state of the code

- Submitting a fix

- Proposing new features

- Becoming a maintainer

## All Changes Happen Through Pull Requests

Pull requests are the best way to propose changes. We actively welcome your pull requests:

1. Fork the repo and create your branch from `master`.

1. If you've added code that should be tested, add some tests' example.

1. If you've changed APIs, update the documentation.

1. Issue that pull request!

## Local Development

To run & test github-readme-stats you need to follow few simple steps :-

_(make sure you already have a [vercel](https://vercel.com/) account)_

1. Install [Vercel CLI](https://vercel.com/download)

1. Fork the repository and clone the code to your local machine

1. Run the command "vercel" in the root and follow the steps there

1. Create a `.env` file in the root of the directory

1. In the .env file add a new variable named "PAT" with your [github Personal access token](https://docs.github.com/en/github/authenticating-to-github/creating-a-personal-access-token)

1. Run the command "vercel dev" to start a development server at https://localhost:3000

## Themes Contribution

Github readme stats supports custom theming and you can also contribute new themes!

All you need to do is edit [themes/index.js](./themes/index.js) file and add your theme at the end of the file.

While creating the Pull request to add a new theme **don't forget to add a screenshot of how your theme looks**, you can also test how it looks using custom url parameters like `title_color`, `icon_color`, `bg_color`, `text_color`

> NOTE: If you are contributing your theme just because you are using it personally, then you can [customize the looks](./readme.md#customization) of your card with URL params instead.

## Any contributions you make will be under the MIT Software License

In short, when you submit changes, your submissions are understood to be under the same [MIT License](http://choosealicense.com/licenses/mit/) that covers the project. Feel free to contact the maintainers if that's a concern.

## Report issues/bugs using Github's [issues](https://github.com/anuraghazra/github-readme-stats/issues)

We use GitHub issues to track public bugs. Report a bug by [opening a new issue](https://github.com/anuraghazra/github-readme-stats/issues/new/choose); it's that easy!

### Bug Reports

**Great Bug Reports** tend to have:

- A quick summary and/or background

- Steps to reproduce

  - Be specific!

  - Share the snapshot, if possible.

  - Github Readme Stats' live link

- What actually happens

- What you expected would happen

- Notes (possibly including why you think this might be happening, or stuff you tried that didn't work)

People _love_ thorough bug reports. I'm not even kidding.

### Feature Request

**Great Feature Requests** tend to have:

- A quick idea summary

- What & why you wanted to add the specific feature

- Additional Context like images, links to resources to implement the feature etc etc.

## License

By contributing, you agree that your contributions will be licensed under its [MIT License](./LICENSE).