Extracting code from content, e.g loading a book that has computational notebook sections #69

Example

fetch("https://fabien.benetou.fr/Analysis/BeyondTheCaseAgainstBooks?action=source")
.then( r => r.text() )
.then(data => { 
	let code = data.split("\n").filter( l => (l.slice(0,2) == "[@") )[0].slice(2).slice(0,-2);
    console.log(code) 
} )

As described in https://fabien.benetou.fr/Analysis/BeyondTheCaseAgainstBooks

Added as 9b2dd9284c