[ci skip] Add contribution doc

CONTRIBUTING.md

@@ -0,0 +1,51 @@
+# Contributing
+
+Thanks for your interest in contributing to Asynq!
+We are open to, and grateful for, any contributions made by the community.
+
+## Reporting Bugs
+
+Have a look at our [issue tracker](https://github.com/hibiken/asynq/issues). If you can't find an issue (open or closed)
+describing your problem (or a very similar one) there, please open a new issue with
+the following details:
+
+- Which versions of Go and Redis are you using?
+- What are you trying to accomplish?
+- What is the full error you are seeing?
+- How can we reproduce this?
+  - Please quote as much of your code as needed to reproduce (best link to a
+    public repository or Gist)
+
+## Getting Help
+
+We run a [Gitter
+channel](https://gitter.im/go-asynq/community) where you can ask questions and
+get help. Feel free to ask there before opening a GitHub issue.
+
+## Submitting Feature Requests
+
+If you can't find an issue (open or closed) describing your idea on our [issue
+tracker](https://github.com/hibiken/asynq/issues), open an issue. Adding answers to the following
+questions in your description is +1:
+
+- What do you want to do, and how do you expect Asynq to support you with that?
+- How might this be added to Asynq?
+- What are possible alternatives?
+- Are there any disadvantages?
+
+Thank you! We'll try to respond as quickly as possible.
+
+## Contributing Code
+
+1. Fork this repo
+2. Download your fork `git clone https://github.com/your-username/asynq && cd asynq`
+3. Create your branch `git checkout -b your-branch-name`
+4. Make and commit your changes
+5. Push the branch `git push origin your-branch-name`
+6. Create a new pull request
+
+Please try to keep your pull request focused in scope and avoid including unrelated commits.
+
+After you have submitted your pull request, we'll try to get back to you as soon as possible. We may suggest some changes or improvements.
+
+Thank you for contributing!

README.md

@@ -119,6 +119,11 @@ go get -u github.com/hibiken/asynq/tools/asynqmon
 
 For details on how to use the tool, refer to the tool's [README](/tools/asynqmon/README.md).
 
+## Contributing
+
+We are open to, and grateful for, any contributions (Github issues/pull-requests, feedback on Gitter channel, etc) made by the community.
+Please see the [Contribution Guide](/CONTRIBUTING.md) before contributing.
+
 ## Acknowledgements
 
 - [Sidekiq](https://github.com/mperham/sidekiq) : Many of the design ideas are taken from sidekiq and its Web UI