Grapheme.split chops off the skull from the pirate flag

[ageron]

This must be the weirdest issue name I've ever submitted! 😂

Here's a little program to reproduce the issue:

app [main] {
    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.15.0/SlwdbJ-3GR7uBWQo6zlmYWNYOxnvo8r6YABXD-45UOw.tar.br",
    unicode: "https://github.com/roc-lang/unicode/releases/download/0.1.2/vH5iqn04ShmqP-pNemgF773f86COePSqMWHzVGrAKNo.tar.br",
}

import unicode.Grapheme
import pf.StdOut

main =
    result = Grapheme.split "🏴‍☠️🏁🎌🚩🏳️‍🌈"
    StdOut.line! (result |> Inspect.toStr)

The output is:

(Ok ["🏴‍️", "🏁", "🎌", "🚩", "🏳️‍🌈"])

But it should be:

(Ok ["🏴‍☠️", "🏁", "🎌", "🚩", "🏳️‍🌈"])

The pirate flag is composed of three code-points: 🏴 (black flag), \u200d (zero width joiner), and ☠️ (skull), but Grapheme.split drops the ☠️ codepoint, preserving only the first two (the second is invisible, but it's there, I checked).