Add extension docs, update README, and more doc clean up

[SanjulaGanepola]

Changes

• Add search bar
• Add secondary side bar
• Add plugins for code syntax highlighting
• Update CLI docs
• Update all READMEs
• Add extension docs

[SanjulaGanepola]

@worksofliam FYI, the content on the docs site's main page (docs\README.md) is the same as the extension's landing page (vs\README.md). As for the CLI's landing page (docs\README.md), it is also the same but with the Features section replaced with the General Usage section from the docs.