add contribution information

Author: Mordil

CONTRIBUTING.md

@@ -0,0 +1,25 @@
+## Legal
+
+By submitting a pull request, you represent that you have the right to license your contribution to the community, and agree by submitting the patch
+that your contributions are licensed under the [Apache 2.0 license](https://www.apache.org/licenses/LICENSE-2.0.html) (see [`LICENSE`](../LICENSE)).
+
+## Submitting a Bug
+
+Please ensure to specify the following:
+
+* NIORedis commit hash
+* Simplest possible steps to reproduce
+    * A pull request with a failing test case is preferred, but it's just as fine to write it in the issue description
+* Environment Information
+  * For example, are you running in Docker? How are you connecting to it through Docker? What version of Docker?
+  * OS version and output of `uname -a`
+  * Swift version or output of `swift --version`
+  
+## Submitting a Pull Request
+  
+A great PR that is likely to be merged quickly is:
+  
+1. Concise, with as few changes as needed to achieve the end result.
+1. Tested, ensuring that regressions aren't introduced now or in the future.
+1. Documented, adding API documentation as needed to cover new functions and properties.
+1. Accompanied by a [great commit message](https://chris.beams.io/posts/git-commit/)

README.md

@@ -41,3 +41,15 @@ let result = try connection.set("my_key", to: "some value")
 
 print(result) // Optional("some value")
 ```
+
+## Contributing
+
+Check out [CONTRIBUTING.md](CONTRIBUTING.md) for more information on how to help with NIORedis.
+
+It is highly recommended to use [Docker](https://docker.com) to install Redis locally.
+
+```bash
+docker run -d -p 6379:6379 --name nioredis redis:5
+```
+
+Otherwise, install Redis directly on your machine from [Redis.io](https://redis.io/download).