Overview what am installing upgrade

[jwafu]

Getting this page to support more info without leaving the page and also links to other info if needed before downloading.

• [x] get all sections added to the what-am-i-installing page
• [ ] update the internals to support links to other pages (features mainly)
• [x] ensure styling checks out
• [x] review copy

[docs-page[bot]]

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docs.pieces.app/~40

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