IFileSignature: Make FileExtensions a list of string again so that duplication isn't needed for multiple same-format file extensions
IFileSignature: Make FileExtensions a list of string again so that duplication isn't needed for multiple same-format file extensions

RonnChyran/snowflake,RonnChyran/snowflake,SnowflakePowered/snowflake,SnowflakePowered/snowflake,RonnChyran/snowflake,SnowflakePowered/snowflake