add CONTRIBUTING guide

define contributing guide with general guidelines.

Signed-off-by: adrianc <adrianc@nvidia.com>

Author: adrianchiris

CONTRIBUTING.md

@@ -0,0 +1,41 @@
+# Contirbution Guidelines
+
+netlink accepts contributions via GitHub pull requests. This document outlines some of the conventions on how to contribute
+code to the project
+
+## General
+
+* One commit per PR.
+* A PR covers a single area/functionality (e.g  extension of devlink command and link command should go in separate PRs )
+* Each PR should be covered by unit tests when applicable.
+* The goal of Netlink package is to follow iproute2 behavior. when in doubt refer to iproute2 [source code](https://github.com/iproute2/iproute2).
+
+## Code Style
+
+Please follows the standard formatting recommendations and language idioms set out in [Effective Go](https://golang.org/doc/effective_go.html)
+and in the [Go Code Review Comments wiki](https://github.com/golang/go/wiki/CodeReviewComments).
+
+## Commit Message Style
+
+Each commit is expected to comply with the following format:
+
+```
+Change summary
+
+More detailed explanation of your changes: Why and how.
+Wrap it to 72 characters.
+See [here] (http://chris.beams.io/posts/git-commit/)
+for some more good advices.
+```
+
+For example:
+
+```
+Fix poorly named identifiers
+  
+One identifier, fnname, in func.go was poorly named.  It has been renamed
+to fnName.  Another identifier retval was not needed and has been removed
+entirely.
+``` 
+
+> __Note:__ [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/#summary) style is not enforced however is alowed