Adds 'Used by these companies' to splash page

[samredai]

This adds a graphic to the end of the landing-page in a section titled "Well Supported, Widely Adopted" and displays logos of companies who have either contributed to the Iceberg project or who have adopted Iceberg internally.

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Linking #17 #18 #19 #20 and #21 (this PR)

I couldn't create an issue so I just wanted to mention here that all of the above linked PRs are part of a single effort to create a compelling landing-page. In the current state there are no expected merge conflicts and the commits from all of the PRs are collectively deployed to a dev version of the site here where you can see the final state. Big thanks to @djamegoldston for brainstorming on these with me and sharing some pretty cool tools!

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Here is an image of with this PR specifically adds:

[rdblue]

Before we add these, we need to get permission to use the logos. you have my permission to use Tabular, of course. But we should reach out to make sure we can use the others.

[RussellSpitzer]

Yeah don't get me in trouble :), I'll ping the relevant folks for permission (for our company)

[jackye1995]

Also need to verify for the Amazon part, I will update the thread once we get legal approval.

[jackye1995]

Also can consider contacting the following which I saw activities in the community:

• snowflake
• two sigma
• box
• twitter
• auxillo
• tencent
• byte dance

[jackye1995]

@samredai logo usage is approved, with the following requirements:

1. please use a AWS logo instead of Amazon, I can send you a copy to use if you cannot find any.
2. contributor and adopter should not be mixed, as they are different terms legally.