[SocialNetwork] Add CI pipeline

[frotto440]

Here is a CI pipeline which is triggered after every change made to socialNetwork and:

• rebuilds social-network-microservices image,
• calculates the new version,
• tags the image with the new version and pushes to docker hub,
• tags the repository with the new version using "socialNetwork" prefix.

It is required to add two secrets with read/write permissions: DOCKER_REGISTRY_LOGIN and DOCKER_REGISTRY_PASSWORD.