MINOR: Update site docs for ASF compliance (#12494)
This PR is a mirror of apache/kafka-site#433 which used placeholder images for the Kafka Streams that users need to click in order to load the iframe with the corresponding video.
Reviewers: Mickael Maison <mimaison@apache.org>
<h3class="streams_intro">The easiest way to write mission-critical real-time applications and microservices</h3>
<pclass="streams__description">Kafka Streams is a client library for building applications and microservices, where the input and output data are stored in Kafka clusters. It combines the simplicity of writing and deploying standard Java and Scala applications on the client side with the benefits of Kafka's server-side cluster technology.</p>
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<h3>VIDEO TOUR OF THE STREAMS API</h3>
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<spanclass="video-number">1</span><ahref="https://www.youtube.com/embed/Z3JKCLG3VP4"><spanclass="video__text">Intro to Streams</span></a>
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<spanclass="video-number">2</span><ahref="https://www.youtube.com/embed/LxxeXI1mPKo"><spanclass="video__text">Creating a Streams Application</span></a>
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<pclass="video__item video_list_3 active">
<spanclass="video-number">3</span><ahref="https://www.youtube.com/embed/7JYEEx7SBuE"><spanclass="video__text">Transforming Data Pt. 1</span></a>
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<spanclass="video-number">4</span><ahref="https://www.youtube.com/embed/3kJgYIkAeHs"><spanclass="video__text">Transforming Data Pt. 2</span></a>