Update README.md

[charliewilco]

fix code fence

Introduction 📟

Purpose ℹ️

Scope 🔭

[macroscopeapp[bot]]

Fix code block formatting in README.md by correcting closing delimiter

Corrects a formatting issue in README.md where a code block example showing client creation with SigningKey was improperly terminated with '``' instead of '```'.

📍Where to Start

Review the changes in README.md to verify the code block formatting correction.

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Macroscope summarized 881d6e4.