Docs: Updated home page with README files & nav changes

[kathancox]

Fixes #835

Updates include:

• Adding the features from the README to the home page
• Creating a known limitations page on the docs site
• Adjustments to nav, the most notable is breaking down the details section into Binaries and Concepts
• Reducing some of the language on the home page for the docs overview that pre-empted what was already in those sections

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[tburgin]

Thanks Kat 🎉 💃