Added string pluralization support example

[fhasse95]

This PR demonstrates the string pluralization support by extending LocalizationPlayground.swift.

Parent PR:

• Added string pluralization support skip-foundation#102

Notes & Limitations:

• Specific forms like "few" or "many" will only trigger if the device itself is set to a locale that supports them (e.g., Ukrainian). Consequently, if a string is formatted using a custom locale that requires additional grammatical forms (like in LocalizationPlayground.swift), these may not be correctly applied if the underlying system locale is set to a language like English, which only supports "zero", "one" and "other" (see screenshots below).
• However, since users typically have their devices set to their native locale, and this behavior is consistent with Apple's documentation for localizedStringWithFormat, I believe this limitation is negligible in practice.

Screenshots:
Device Locale Matching (iOS)

Device Locale Matching (Android):

=> Supports all variants

Device Locale Not Matching (iOS):

Device Locale Not Matching (Android):

=> Supports only "zero", "one" and "other"

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• AI was used to generate or assist with generating this PR. Please specify below how you used AI to help you, and what steps you have taken to manually verify the changes.
  => I used AI assistance while translating the new localized strings.

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