Add more icons

[MrCoder]

Linked issue (mermaid-js/zenuml-core#77) for @zenuml/core.

Add the following icons:

Group 1

1. Client
2. Server
3. Browser
4. Service
5. Controller
6. API (Application Programming Interface)
7. UI (User Interface)
8. Mobile
9. ExternalSystem

Group 2

1. Application
2. LoadBalancer
3. Network
4. Cache
5. WebServer
6. MessageQueue
7. Scheduler
8. Gateway
9. AuthenticationService
10. MailServer

Group 3

1. GitHub
2. Docker
3. GitLab
4. Jenkins
5. PostgreSQL
6. MongoDB
7. Kubernetes
8. Apache Kafka
9. Elasticsearch
10. Auth0
11. Redis

[nagababu007]

Hi @MrCoder , Can this also be closed ? Looks like this is sub issue of issue#77 - mermaid-js/zenuml-core#77

[MrCoder]

@nagababu007 , this ticket is for docs. The code base is not quite ready. So I have moved this to backlog.