feat(prompts): add "Code Explainer for Juniors" prompt

[antonin-tacchi]

Add Code Explainer For Junior

Added a new prompt for tightly scoped code explanations for juniors based on a given [SUBJECT] and [CODE]. It enforces 5 numbered points with a)–d) sub-points, adds "(off-topic)" when a detail exceeds [SUBJECT], and allows a minimal 1–3 line fix block only if a bug impacts the subject—no intro, no conclusion, no jargon, backticks only for identifiers, and answers in the prompt’s language.

Checklist

• I've confirmed the prompt works well
• I've added
  Contributed by: [@yourusername](https://github.com/yourusername)
• I've added to the README.md
• I've added to the prompts.csv
  • Escaped quotes by double-quoting them
  • No spaces after commas after double quotes. e.g. "Hello","hi", not
    "Hello", "hi"
  • Removed "Act as" from the title on CSV

This prompt helps mentors deliver tightly scoped, junior-friendly code explanations by enforcing a strict 5-point structure with a)–d) sub-points, optional minimal fix blocks only for subject-impacting bugs, automatic “(off-topic)” tagging, and no intro/conclusion/jargon—backticks reserved for identifiers.

[CoronaDaniel]

Thanks for sharing the mega prompt is awesome, but I usually work in imagen and video generation (JSON) for VEO3, my question is about if I could adapt the mega prompt for my proposes as AI Designer? Thanks.

[antonin-tacchi]

I don't mind, but will my PR be accepted and will I get a “contribution” or “credit” on your VEO3 project?
To be honest, this is my first PR Open source.

[f]

Can you change variables to "${key:default_value}" format instead of [Subject]? e.g. ${Subject:JavaScript}