fix: pick new random quote per call and correct index bounds (by Basuki)

[basukinath]

• Fixes a bug where the library selected a single random quote once at module load and returned the same quote for every call.
• Ensures a fresh random quote is selected on each call to getQuote() and getRandomQuote().
• Corrects the random index bounds (uses 0..arr.length-1).
• Adds a small file header attribution: "Contributed by Basuki".

Why this change

• Users expect random APIs to return different values across calls. The previous behavior was surprising and effectively non-random for the lifetime of the process.
• The off-by-one in the index generation could potentially select an out-of-range index in some implementations; the fix makes the behavior robust.

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