Rehaul docs, add tutorial section

[andrewjong]

Documentation Overhaul. Need to add a big CAVEAT that AirStack is alpha stage and not yet meant for outside-CMU

• Tutorials: walkthroughs for users
• “Getting Started:”
• “Your First Sim Run with Software-in-the-Loop”
• “Your First Sim Run with Hardware-in-the-Loop” (AGX, GCS, Isaac-sim desktop)
• “Your First Real World Flight”
• “Customize AirStack for Your Needs”
• “How to Fork AirStack”
• how to setup your own documentation website
• how to pull in upstream changes
• “Create a Custom Isaac-Sim Scene”
• “Customize Launch Parameters”
• “Swap In Your Own Autonomy Modules”
• “How to Write Documentation”
• Advanced
• “Introduction to TAK Integration”
• “How to Contribute Back to AirStack”
• Documentation: detailed documentation about parameters and algorithms