docs: add simple 'add' case to clarify setup.
docs: add simple 'add' case to clarify setup.

This patch adds a simple use case for adding a library to an existing
repository.

Signed-off-by: Dan Sabath <4d4506b6d9bab2083d550dabcad59f7a02d8b290@whitepages.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git