[docs] Add Assets guide to Home

[amandeepmittal]

Why

Follow up #28261

How

• Update the outdated Assets guide

• Add it to Home > Develop > User Interface

• Add info on how to load local assets using expo-assets config plugin
  

• Remove duplicated info on optimizing images manually from Expo Updates Assets guide and update the section in Assets guide since this guide comes first in the hierarchy

• Update Fonts guide to add a section on initial loading expo/vector-icons package

• Update navigation.js file and add redirects for the new URL

Test Plan

Run docs locally and visit: http://localhost:3002/develop/user-interface/assets/, or see Preview: http://docs.expo.dev-pr-28331.s3-website-us-east-1.amazonaws.com/develop/user-interface/assets/

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• Conforms with the Documentation Writing Style Guide
• This diff will work correctly for npx expo prebuild & EAS Build (eg: updated a module plugin).

[expo-bot]

📘 Your docs preview website is ready!

[jonsamp]

Loved the assets docs and learned some things! Left some comments on things i would change. Thanks for writing this up.