[Website] Replace Slides/Cards in Carousel and Add Links

1) Add a button "Learn more" with an arrow on each card: 

2) Replace content in cards: 

Card 1: 

Text: Seznam, a Czech search engine, has been an early contributor and adopter of Apache Beam, and they migrated several petabyte-scale workloads to Apache Beam pipelines.
Learn more (link: https://beam.apache.org/case-studies/seznam/)

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Card 2: 

Text: Palo Alto Networks, Inc. is a global cybersecurity leader that uses Apache Beam to process ~10 millions of security log events per second for their real-time streaming infrastructure.

Learn more (link: https://beam.apache.org/case-studies/paloalto/ )

Logo:

Card 3: 
Text: Apache Beam provides Ricardo, a leading Swiss second hand marketplace, with a scalable and reliable data processing framework that supports fundamental business scenarios and enables real-time and ML data processing. 

Learn more (link: https://beam.apache.org/case-studies/ricardo/  )

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Card 4: 

Text: Apache Hop, an open-source data orchestration platform, uses Apache Beam to "design once, run anywhere" and creates a value-add for Apache Beam users by enabling visual pipeline development and lifecycle management.
Learn more (link: https://beam.apache.org/case-studies/hop/ )
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Card 5: 
Text:

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Share your story (link: dev@beam.apache.org?subject=Beam Website Add New Case Study)