`Documentation`: Update documentation of Apollon

[minrows]

Motivation and Context

The current documentation of Apollon, found here, is outdated and hence needs an update.

Description

This PR simply updates the documentation of Apollon.

Steps for Testing

In local machine

1. Clone the repo and checkout to the documentation/update-documentation branch.
2. Goto docs/ folder and install all the python dependencies by executing pip install -r requirements.txt
3. Finally execute make singlehtml command
4. Goto docs/build/singlehtml folder and open index.html in your browser.
5. Observe the updated documentation.

From Artifact

You can also test the documentation from the latest build here.

PS: For more information regarding building the documentation, please refer to Artemis Documentation.