content: Add new questions to reach 20 per world

[albertoivo]

This PR adds new educational content to the basic_commands, user_input, dictionaries, and error_handling worlds to meet the minimum requirement of 20 questions per world. The new questions cover various difficulty levels and concepts appropriate for the target age group, following the existing QuestionDocument structure. All changes were verified with existing tests.

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PR created automatically by Jules for task 11560812229656382058 started by @albertoivo

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