[CON-16] Write Docusaurus docs

[sestinj]

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_CON-16

[TyDunn]

@sestinj Proposed initial structure:

• Landing page (name, one line description, 3x on sentence descriptions about why to use Continue)
• Introduction (what is Continue, why to use it, how to get started)
• Getting started (steps to try out Continue using GitHub Codespaces with our best example)
• Installation (push everyone through using Continue packaged as a VS Code extension for now, via source)
• Walkthroughs (How to use GUI, How to use a recipe, How to create a recipe, How to share a recipe, etc)
• Concepts (explanations of all the key aspects: steps, recipes, GUI, SDK, etc)
• SDK (explanations of all of the methods, etc)
• Telemetry (we track anonymously, this is what we track, this is how you can opt out)