docs: Revamp Docs for V1.0.2

[gabrielle-ong]

Top priority:

• Cortex.cpp readme
  • remove tensorrt
  • add basic usage
• Models page - Comment out Onnx and Tensorrt models, remove :gguf variant
• Quickstart page:
  cortex pull
  cortex engines install llama.cpp(if needed)
  cortex run
  model ps
  model stop
  cortex update
  cortex stop
  Less priority:
• Model variants table like ollama - I will remove the model variants column because we support 10+ variants, not 1 as listed in the table
• Change installation links to latest (currently is releases)
• move all the cortex-nightly cortex-beta to 1 section, currently we x3 all commands in all pages

Out of scope

• binary links add to github readme
• Changelog
• Upcoming features eg engines management

Subsequent PR

• CLI commands
• Docker command
• Network vs Local Installer (in Advanced Installation)