SDK for Embedding dashboards

[kormpakis]

[SIP] Proposal for better documentation<title>

Motivation

The documentation is really bad.
There should be an easy and straightforward way to let us understand what is needed, all in one page.
The docs don't even mention how to acquire an access token, or how to make the charts embeddalby by changing the superset_config.py.

Proposed Change

Please update the docs.