setup CI/CD

[bambooSocks]

• setup CI on the backend
• setup CD on the backend
• setup CI on the frontend
• setup CD on the frontend

[Krismix1]

Frontend CI pipeline: automatic-potato/linkedin-clone-frontend#3
Frontend CD pipeline: automatic-potato/linkedin-clone-frontend#2
Backend CI pipeline: automatic-potato/linkedin-clone-backend#4
Backend CD pipeline: automatic-potato/linkedin-clone-backend#3