Update CONTRIBUTING.md (#128)

* init contributing guide
* update README

Signed-off-by: Lee <lee10202013@gmail.com>
Co-authored-by: Charlie Jonas <charlie@charliejonas.co.uk>

CONTIBUTING.md

@@ -0,0 +1,44 @@
+# Contributing
+
+First off, thanks for taking the time to contribute!
+
+Remember that this is open source software so please consider the other people who will read your code.
+Make it look nice for them, document your logic in comments and add or update the unit test cases.
+
+This library is used by various other projects, companies and individuals in live production environments so please discuss any breaking changes with us before making them.
+Feel free to join us in the #go-ping channel of the [Gophers Slack](https://invite.slack.golangbridge.org/).
+
+## Pull Requests
+
+[Fork the repo on GitHub](https://github.com/go-ping/ping/fork) and clone it to your local machine.
+
+```bash
+git clone https://github.com/YOUR_USERNAME/ping.git && cd ping
+```
+
+Here is a guide on [how to configure a remote repository](https://docs.github.com/en/free-pro-team@latest/github/collaborating-with-issues-and-pull-requests/configuring-a-remote-for-a-fork).
+
+Check out a new branch, make changes, run tests, commit & sign-off, then push branch to your fork.
+
+```bash
+$ git checkout -b <BRANCH_NAME>
+# edit files
+$ make style vet test
+$ git add <CHANGED_FILES>
+$ git commit -s
+$ git push <FORK> <BRANCH_NAME>
+```
+
+Open a [new pull request](https://github.com/go-ping/ping/compare) in the main `go-ping/ping` repository.
+Please describe the purpose of your PR and remember link it to any related issues.
+
+*We may ask you to rebase your feature branch or squash the commits in order to keep the history clean.*
+
+## Development Guides
+
+- Run `make style vet test` before committing your changes.
+- Document your logic in code comments.
+- Add tests for bug fixes and new features.
+- Use UNIX-style (LF) line endings.
+- End every file with a single blank line.
+- Use the UTF-8 character set.

README.md

@@ -135,3 +135,7 @@ This repo was originally in the personal account of
 For support and help, you usually find us in the #go-ping channel of
 Gophers Slack. See https://invite.slack.golangbridge.org/ for an invite
 to the Gophers Slack org.
+
+## Contributing
+
+Refer to [CONTRIBUTING.md](https://github.com/go-ping/ping/blob/master/CONTRIBUTING.md)