Improve the style of the examples

[jorgepiloto]

The examples in https://hps.docs.pyansys.com/version/stable/examples/ are not executed but directly included within the rST pages. Although not ideal, this is still acceptable.

The problem is that they render as a table. This table has on its left a the name of the file and on its right the actual code. Furthermore, the download buttons are not as explicit as in other libraries, see https://geometry.docs.pyansys.com/version/stable/examples.html