Unable to encode high-byte order Unicode characters

[deed02392]

There seems to be an issue with the Unicode character handling.

I am able to encode ↘ for example which is U+2198
Raw bytes encoded are:
40 7e fb bb fe 28 69 82 00 ec 11 ec 11 ec 11 ec

However a larger Unicode character 🔝 is U+1F51D

This gets encoded with the following raw bytes:
40 9e fb bb fe da 0b de db 49 d0 ec 11 ec 11 ec

Somehow this is not correct because of a failure to reproduce the Unicode character, although I'm still unsure exactly what the failure is, I suspect it is in QR8BitByte().

[deed02392]

This is a correct raw byte sequence for encoding "🔝":

71 a4 04 f0 9f 94 9d 00 ec 11 ec 11 ec 11 ec 11
ec 11 ec

It looks like qrbtf does not support Mode 7.

Here's a valid byte sequence with Mode 4:

40 4f 09 f9 49 d0 ec 11 ec 11 ec 11 ec 11 ec 11
ec 11 ec

[deed02392]

The issue seems to be the encoding algorithm is for UTF-8 code units, but charCodeAt gets UTF-16 code units. The encoding algorithm used in QR8BitByte() is only a partial implementation of https://github.com/akheron/jansson/blob/master/src/utf.c

I suggest we use an external library to make more reliable encoding of input strings.

[pemontto]

Just ran into this issue trying to add my WiFi
WIFI:S:🐙 🐒;T:WPA;P:<redacted password>;;