Proofreading and design update

[yuxizama]

Language

Proofreading has been done through all the contents in "Get Started", "Fundamentals", "Guides", and "Tutorials", the main changes are :

• Rephrased sentences to improve readability
• Transform some complex ideas into lists
• Aligned all formats in headings and texts
• Added an introduction at the beginning of each doc More details can be found in the WIP Zama Doc Style Guide

⚠️ Note that the proofreading is purely language modifications (as I don't understand the technical details of TFHE-rs). Please review and correct in case my rephrases change some technical implications.

Design

I updated the card image design on the landing page based on Rand's requirement here. The main changes are:

• Add icons in the card images
• Unify the card size by adjusting the text in order to harmonize the mobile display