Maintain the sphinx design

[Revathyvenugopal162]

Before patch,

• add fading around the cards on dark theme
• make the cards are of same size irrespective of text size

• before : https://docs.pyansys.com/index.html
• After :
  
  

[jorgepiloto]

Just to make sure, this pull-request allows to display some fading light around the cards, right?

[Revathyvenugopal162]

Just to make sure, this pull-request allows to display some fading light around the cards, right?

yes and also the cards are in same size, irrespective of the text inside.

[MaxJPRey]

Very nice improvement @Revathyvenugopal162 .