add contributing (#135)

Author: ardalis

CONTRIBUTING.md

@@ -0,0 +1,46 @@
+# Contributing to Ardalis.GuardClauses
+
+We love your input! We want to make contributing to this project as easy and transparent as possible, whether it's:
+
+- Reporting a bug
+- Discussing the current state of the code
+- Submitting a fix
+- Proposing new features
+
+## We Develop with GitHub
+
+Obviously...
+
+## We Use Pull Requests
+
+Mostly. But pretty much exclusively for non-maintainers. You'll need to fork the repo in order to submit a pull request. Here are the basic steps:
+
+1. Fork the repo and create your branch from `main`.
+2. If you've added code that should be tested, add tests.
+3. If you've changed APIs, update the documentation.
+4. Ensure the test suite passes.
+5. Make sure your code lints.
+6. Issue that pull request!
+
+- [Pull Request Check List](https://ardalis.com/github-pull-request-checklist/)
+- [Resync your fork with this upstream repo](https://ardalis.com/syncing-a-fork-of-a-github-repository-with-upstream/)
+
+## Ask before adding a pull request
+
+You can just add a pull request out of the blue if you want, but it's much better etitquette (and more likely to be accepted) if you open a new issue or comment in an existing issue stating you'd like to make a pull request.
+
+## Getting Started
+
+Look for [issues marked with 'help wanted'](https://github.com/ardalis/guardclauses/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22) to find good places to start contributing.
+
+## Any contributions you make will be under the MIT Software License
+
+In short, when you submit code changes, your submissions are understood to be under the same [MIT License](http://choosealicense.com/licenses/mit/) that covers this project.
+
+## Report bugs using Github's [issues](https://github.com/ardalis/guardclauses/issues)
+
+We use GitHub issues to track public bugs. Report a bug by [opening a new issue](https://github.com/ardalis/GuardClauses/issues/new/choose); it's that easy!
+
+## Sponsor us
+
+If you don't have the time or expertise to contribute code, you can still support us by [sponsoring](https://github.com/sponsors/ardalis).