docs: update README with contribution guidelines
docs: update README with contribution guidelines

This patch simply adds a section for the Contribution Guidelines.

Signed-off-by: Renato Lui Geh <6f991c0560e5a20ed79f442e86dbd5a61a5f5796@gmail.com>

RenatoGeh/gospn,RenatoGeh/gospn,RenatoGeh/gospn