Added is_kebab_case utility in string class

[suryapratapsinghsuryavanshi]

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• Fix a bug or typo in an existing algorithm?
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[priya-sundaram-dev]

Thanks for the contribution, @suryapratapsinghsuryavanshi. One correctness issue worth fixing before this can land:

re.match only anchors at the start of the string, so trailing junk slips through:

>>> is_kebab_case("variable-name!!!")
True   # should be False

Use re.fullmatch (or add a $ anchor) so the whole string must match. While you are at it, you can drop the separate "_" not in var_name guard and the \w hack by matching lowercase kebab directly, which also correctly rejects Variable-Name (kebab-case is conventionally lowercase):

return bool(re.fullmatch(r"[a-z0-9]+(?:-[a-z0-9]+)+", var_name))

Could you also add doctests for the trailing-character case and an uppercase input? Happy to re-review once updated.