Update locale for [NL]

[Dutchguy1982]

Added the dutch translation for the three new additions

        "INVALID_ACCOUNT": "Invalid account",
        "INVALID_PASSWORD": "Invalid password",
        "USERNAME_TAKEN": "Username is already taken"

Also searched and added al the enters, so the file is 100% accurate with the EN.json

Description

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Checklist

Please ensure your PR meets the following requirements:

• Changes are limited to one locale file.
• JSON file is properly formatted with 4-space indentation.
• The JSON file has been validated for syntax errors.
• The PR title clearly describes the locale and nature of the changes (e.g., "Update French Translations").

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Related Issues or Discussions

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[Maximus7474]

Thanks !