MG-8 - Add Developer Sidebar and Quick Start Guide

[Musilah]

Pull request title should be MG-XXX - description or NOISSUE - description where XXX is ID of issue that this PR relate to.
Please review the CONTRIBUTING.md file for detailed contributing guidelines.

What does this do?

• Adds a developer's guide sidebar to the documentation
• Adds the getting started guide for developers using CLI
• Updates the CLI documentation
• Restructures the Getting Started flow
• Update Entities file

Which issue(s) does this PR fix/relate to?

Related to #8

List any changes that modify/break current functionality

Have you included tests for your changes?

Did you document any new/modified functionality?

Notes

[ianmuchyri]

Let's have this here:

As well as an external link to the api docs

Also try out with User Docs and Dev Docs, see if they look better. These ones seem too long. But I don't know what the convention is

[ianmuchyri]

Also can we split docs into two,

1. user
2. dev

So say endpoints for clients in users will be /user/clients then for developer docs will be /dev/clients.
It will also make it easy to know which docs are for user-docs and which are for dev-docs

[ianmuchyri]

1. Can we have the title as Introduction as well
   

2. Should we be using specific people names? Like celebrities for example
   

3. We should also talk about clients and channels management using the cli
   

4. Also within a particular management we seem to be missing roles, and user management in details. Or is this not supported by the cli?
   

5. This section isn't up to date. All these are individual services under the new architecture. Check on that. This may necessitate an pr on it's own as it involves a lot . The structs have also changed. Also I think this file should come second after getting started, so the user knows the entities they are working with.
   

[ianmuchyri]

1. Is role meant to be under users, or on it's own?
   

2. Only users have roles
   

3. Just have it as Overview
   

4. Just Introduction is enough
   

5. Move Entities to just after getting started