Improve documentation sections

[RobPasMue]

At the moment the docs are a clean sheet. We should consider implementing the basic sections of all PyAnsys docs:

• Improve the Examples section of the documentation #141
• Add a Getting started section to the documentation #142
• Improve API reference in the docs #143
• Add a User guide section to the docs #144
• Add a Contributing section to the docs #145

[RobPasMue]

They don't have to be full of information. It's just creating the structure. Except for Getting started.

[jorgepiloto]

Let me work on this.

What do you think about using https://sphinx-autoapi.readthedocs.io/en/latest/? I will save us a lot of time, as the API reference gets automatically generated. No need to have any RST files, everything builds on the fly when rendering the docs.

[MaxJPRey]

@jorgepiloto Yes based on the limited amount of time we have, we can set this up first.
Then we can setup a "regular/usual" pyansys doc later.

[RobPasMue]

That'd be great @jorgepiloto, we can always come back to it later. Thanks!!