New output format: Self-XHR/Fetch (-F8xhr, -F8fetch)

[lifthrasiir]

xem's int2binary2html gives three approaches to encode binary data. The second is based on single-byte encoding (#31), the third is not as efficient as the current six-bit encoding (documented in #29), but the first is based on XHR/fetch which can be compatible over many settings.

The modus operandi is as follows: the HTML contains a hidden chunk of binary data (which can be interpreted as U+FFFD by browsers). JS then reads the HTML file itself as an ArrayBuffer and extract required bytes. The decoder would then look like this:

with(new XMLHttpRequest)open('GET','#'),responseType='arraybuffer',send(),onload=r=>{...} // XHR
fetch('#').then(r=>r.arrayBuffer()).then(r=>{r=new Uint8Array(r);...}) // fetch