Add .md to README and clarify what example does#712

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mjcross wants to merge 5 commits intoraspberrypi:developfrom

mjcross:develop

Commits on Oct 2, 2025

Add .md to README and clarify what example does
Martin Crossley
committed

Commits on Oct 9, 2025

Improve comments in mqtt_client example
Martin Crossley
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Commits on Oct 10, 2025

fix typo in comment
Martin Crossley
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Commits on Nov 13, 2025

protect call to lwIP mqtt_client_new()
Martin Crossley
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only poll cyw43_arch() in main() if we are in polling mode
Martin Crossley
committed