Added videos and articles

Signed-off-by: Zhou Fang zhou.fang@eclipse-foundation.org

content/resources/articles/2021-08-02-mqtt-and-the-purdue-model-iiot-security-best-practices.md

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+date = "2021-08-02"
+title = "MQTT and the Purdue Model: IIoT Security Best Practices"
+link = "https://cirrus-link.com/mqtt-and-the-purdue-model-iiot-security-best-practices/"
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+The Purdue Model of Computer Integrated Manufacturing was published in 1990 as a reference for enterprise architecture – a hierarchical model for manufacturing automation that defines what type of equipment goes where what actions are supposed to happen at each level, and how machines and processes interact.