Revise pass-by-value and pass-by-reference documentation

[shiracamus]

C言語は参照渡しできない言語なのでC++言語のコードに置き換えました。
値渡しと参照渡しの説明を補足してみました。

close #739

---

Note

Rewrites and expands docs/reference/functions/pass-by-value.md to clarify pass-by-value vs pass-by-reference (C++ examples) and JavaScript’s pass-by-value with object sharing behavior.

• Docs: docs/reference/functions/pass-by-value.md
  • Conceptual clarifications:
    • Add section on variable kinds (value vs reference types) and how values/refs are passed.
    • Refine definitions of value-passing (copy vs shared reference copy) and reference-passing (variable sharing).
  • Examples:
    • Replace C samples with C++ implementations for value-pass and reference-pass using int and references; switch output to std::println.
    • Expand JavaScript section: reaffirm all args are pass-by-value; illustrate object sharing, reassignment breaking sharing, and effects in function arguments.
  • Edits: Polish headings/wording and update summary bullet list.

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[tats-u]

※printlnはC++23

https://cpprefjp.github.io/reference/print/println.html

[tats-u]

値型の方もC++23に書き換える場合

[tats-u]

模範的なコードなのでreturn 0;はあったほうがいいですね(なんで今までなかったんだ・・・)

[shiracamus]

Prettierでエラーが出ていたので修正しました。