Fix packaging very large projects as HTML files in Chrome (#862)

Actually fixes https://github.com/TurboWarp/packager/issues/528

https://github.com/TurboWarp/packager/pull/861 fixed running large projects
in Chrome, but packaging still used string concatenation so it remained broken.
Now the concatenation part is done using TextEncoder & Uint8Arrays and a
template tag function to keep it readable.

This time I have actually tested it with a 1.0GB sb3.

Breaking Node API change: The data property returned by Packager#package() is
now always a Uint8Array instead of sometimes string and sometimes ArrayBuffer.

node-api-docs/README.md

@@ -126,7 +126,7 @@ const filename = result.filename;
 // MIME type of the packaged project. Either "text/html" or "application/zip"
 const type = result.type;
 
-// The packaged project's data. Will be either a string (for type text/html) or ArrayBuffer (for type application/zip).
+// The packaged project's data. Will always be a Uint8Array.
 const data = result.data;
 ```