Highlighting emojis in Text tags is showing strange Glyphs �

[jheyming]

Describe the bug

If you have emojis in Text data, highlighting them generates glyphs �

I found that if I turn off FF_LSDV_4620_3, the issue goes away:

The issue seems to be

        self._spans = self.parent.createSpansByGlobalOffsets(self.globalOffsets);

https://github.com/HumanSignal/label-studio/blob/develop/web/libs/editor/src/mixins/HighlightMixin.js#L70

The spans that are generated have strange \u characters.

To Reproduce Steps to reproduce the behavior:

1. Import a task with emojis
2. Make your project have a <Text> tag with <Lables>.
3. Select any label, then highlight the emoji
4. see the glyph

Expected behavior The emojis are properly highlighted

Screenshots If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS: [e.g. iOS]
• Label Studio Version [e.g. 0.8.0]

Additional context Add any other context about the problem here.