Bug with skin tone emojis when using `prevGraphemeClusterBreak` package

There's an issue with `prevGraphemeClusterBreak` package, if I compare the results with `nextGraphemeClusterBreak` for a single skin tone emoji it doesn't return the same values,

```
prevGraphemeClusterBreak( '👉🏿' ) // returns 1
nextGraphemeClusterBreak( '👉🏿' ) // returns -1
```

_Originally posted by @steff456 in https://github.com/stdlib-js/stdlib/pull/1079#discussion_r1306328286_

Start by reproducing the discrepancy with the `prevGraphemeClusterBreak` and `nextGraphemeClusterBreak` entry points using the single skin tone emoji shown in the issue. Compare their boundary results and inspect the related package behavior; done means the two functions handle this emoji consistently and the regression is covered by a test.

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