Define chunk size for `ReadableStream` created by `blob::stream()`

Currently regarded as 'Issue 1' I have recently come across a project that forces me to assume the chunk size for the stream. Testing with chromium and firefox, the chunk size appears to be 0x10000 or 65536. I cannot find a reason why it's this particular number.

As I'm making a wasm module, I must allocate memory space when going through files 5GB+ in size. I will allocate 0x10000 bytes for now, but only out of assumption... if there's a browser out there that does not follow this assumption then there will be fatal bugs.

I'm not sure if this is w3c/FileAPI/'s or streams.spec.whatwg.org's jurisdiction. But neither of them has an exact number.

Inizia da questa issue e confronta le sezioni delle specifiche File API e Streams citate nella discussione. Determina quale specifica è responsabile del comportamento della dimensione dei chunk di ReadableStream e se è possibile specificare un valore fisso 0x10000; il lavoro è completato quando la specifica responsabile e il requisito normativo sono concordati e documentati.