Migration/Getting started page

[germa89]

Migration: Document converter as a tool for transition from MAPDL scripts to PyMAPDL.

Ideally, we should be more explicit about this on the documentation, maybe having a section/page with things like:

Getting started
==============

As an MAPDL user
-------------------

If you are an experienced MAPDL user, you should....

As a Python user
-----------------

If this is your fist contact with MAPDL and PyMAPDL, then....

We could explain the different views in each paragraph. Like how important is the gRPC connection and the mapdl.parameters for Pythonic users, and how the non_interactive context manager works for MAPDL users.