Support UTF-16 encoding

[Wernfried]

According to W3C Recommendations every XML processor must be able to read UTF-8 and UTF-16 encodings. A XML file encoded in UTF-16

<?xml version="1.0" encoding="UTF-16"?>
<person>Hi Jérôme</person>

throws an error:

C:\nodejs18\node.exe .\demo.js
error at line [1], column [2] Error: Non-whitespace before first tag.
Line: 0
Column: 1
Char: �
    at error (D:\Internet\xml-twig\node_modules\sax\lib\sax.js:652:10)
    at strictFail (D:\Internet\xml-twig\node_modules\sax\lib\sax.js:678:7)
    at beginWhiteSpace (D:\Internet\xml-twig\node_modules\sax\lib\sax.js:952:7)
    at SAXParser.write (D:\Internet\xml-twig\node_modules\sax\lib\sax.js:1007:11)
    at SAXStream.write (D:\Internet\xml-twig\node_modules\sax\lib\sax.js:240:18)
    at ReadStream.ondata (d:\Internet\xml-twig\lib\internal\streams\readable.js:777:22)
    at ReadStream.emit (d:\Internet\xml-twig\lib\events.js:517:28)
    at addChunk (d:\Internet\xml-twig\lib\internal\streams\readable.js:335:12)
    at readableAddChunk (d:\Internet\xml-twig\lib\internal\streams\readable.js:308:9)
    at Readable.push (node:internal/streams/readable:245:10) {stack: 'Error: Non-whitespace before first tag.
Line:….push (node:internal/streams/readable:245:10)', message: 'Non-whitespace before first tag.
Line: 0
Column: 1
Char: �'}
Uncaught TypeError TypeError: Cannot read properties of undefined (reading 'text')
    at <anonymous> (file:///D:/Internet/xml-twig/twig.js:319:30)
    at emit (node:events:517:28)
    at me._parser.<computed> (file:///D:/Internet/xml-twig/node_modules/sax/lib/sax.js:259:17)
    at emit (file:///D:/Internet/xml-twig/node_modules/sax/lib/sax.js:625:35)
    at closeText (file:///D:/Internet/xml-twig/node_modules/sax/lib/sax.js:635:26)
    at error (file:///D:/Internet/xml-twig/node_modules/sax/lib/sax.js:646:5)
    at strictFail (file:///D:/Internet/xml-twig/node_modules/sax/lib/sax.js:678:7)
    at write (file:///D:/Internet/xml-twig/node_modules/sax/lib/sax.js:1036:15)
    at SAXStream.write (file:///D:/Internet/xml-twig/node_modules/sax/lib/sax.js:240:18)
    at ondata (node:internal/streams/readable:777:22)
    at emit (node:events:517:28)
    at addChunk (node:internal/streams/readable:335:12)
    at readableAddChunk (node:internal/streams/readable:308:9)
    at Readable.push (node:internal/streams/readable:245:10)
    at <anonymous> (node:internal/fs/streams:277:14)
    at wrapper (node:fs:684:5)
    at callbackTrampoline (node:internal/async_hooks:130:17)
    --- FSREQCALLBACK ---
    at init (node:internal/inspector_async_hook:25:19)
    at emitInitNative (node:internal/async_hooks:202:43)
    at read (node:fs:687:15)
    at ReadStream._read (node:internal/fs/streams:250:6)
    at Readable.read (node:internal/streams/readable:507:12)
    at maybeReadMore_ (node:internal/streams/readable:661:12)
    at processTicksAndRejections (node:internal/process/task_queues:82:21)
    --- TickObject ---
    at init (node:internal/inspector_async_hook:25:19)
    at emitInitNative (node:internal/async_hooks:202:43)
    at emitInitScript (node:internal/async_hooks:504:3)
    at nextTick (node:internal/process/task_queues:132:5)
    at maybeReadMore (node:internal/streams/readable:628:13)
    at <anonymous> (node:internal/streams/readable:216:7)
    at onceWrapper (node:events:631:28)
    at emit (node:events:517:28)
    at emitConstructNT (node:internal/streams/destroy:284:10)
    at processTicksAndRejections (node:internal/process/task_queues:81:21)
    --- TickObject ---
    at init (node:internal/inspector_async_hook:25:19)
    at emitInitNative (node:internal/async_hooks:202:43)
    at emitInitScript (node:internal/async_hooks:504:3)
    at nextTick (node:internal/process/task_queues:132:5)
    at onConstruct (node:internal/streams/destroy:270:15)
    at processTicksAndRejections (node:internal/process/task_queues:81:21)
    --- TickObject ---
    at init (node:internal/inspector_async_hook:25:19)
    at emitInitNative (node:internal/async_hooks:202:43)
    at emitInitScript (node:internal/async_hooks:504:3)
    at nextTick (node:internal/process/task_queues:132:5)
    at <anonymous> (node:internal/streams/destroy:276:15)
    at <anonymous> (node:internal/fs/streams:76:9)
    at <anonymous> (node:fs:200:23)
    at callbackTrampoline (node:internal/async_hooks:130:17)
    --- FSREQCALLBACK ---
    at init (node:internal/inspector_async_hook:25:19)
    at emitInitNative (node:internal/async_hooks:202:43)
    at open (node:fs:578:15)
    at _construct (node:internal/fs/streams:71:17)
    at constructNT (node:internal/streams/destroy:275:12)
    at processTicksAndRejections (node:internal/process/task_queues:81:21)
    --- TickObject ---
    at init (node:internal/inspector_async_hook:25:19)
    at emitInitNative (node:internal/async_hooks:202:43)
    at emitInitScript (node:internal/async_hooks:504:3)
    at nextTick (node:internal/process/task_queues:132:5)
    at construct (node:internal/streams/destroy:241:11)
    at Readable (node:internal/streams/readable:214:15)
    at ReadStream (node:internal/fs/streams:214:3)
    at createReadStream (node:fs:3038:10)
    at <anonymous> (file:///D:/Internet/xml-twig/demo.js:6:4)
    at Module._compile (node:internal/modules/cjs/loader:1256:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1310:10)
    at Module.load (node:internal/modules/cjs/loader:1119:32)
    at Module._load (node:internal/modules/cjs/loader:960:12)
    at executeUserEntryPoint (node:internal/modules/run_main:86:12)
    at <anonymous> (node:internal/main/run_main_module:23:47)
Process exited with code 1