ARROW-15684: [Website] Visual identity guidelines for Apache Arrow logo

[djnavarro]

The Apache Arrow logo is not currently documented on the website, and we don't have guidelines about how (or when) people in the community can use adapt it. Now that Arrow is a mature project it would be useful to include this documentation on the site, and to make it easy for people to download "officially supported" versions of the Apache Arrow logo for inclusion in slide decks, websites, etc.

As a related matter, the website currently uses a less-than-ideal image as the social media preview file. There are two limitations: (1) because it uses black text against a transparent background it isn't readable for twitter users with dark mode set (it just looks all black), and (2) it doesn't have wide enough borders, and parts of the logo get cropped out by twitter previews.

To help improve the situation, this PR:

• Documents the visual design of the Apache Arrow logo
• Generates multiple versions of the logo suitable for different contexts
• Provides some guidelines for usage that hopefully aren't too restrictive
• Adds this as a "visual identity" page to the website, and
• Switches the social preview image to one that works on twitter

For a quick preview of what the content of the "visual identity" page would be (minus the formatting), please see:

https://github.com/djnavarro/arrow-visual-identity

[github-actions]

https://issues.apache.org/jira/browse/ARROW-15684

[ianmcook]

This is wonderful, thank you @djnavarro!

How much trouble would it be to include SVG versions of the images under List of provided logo files? The PNG images might have insufficient resolution for some uses such as large-format display or printing, leading to pixelation or poor print quality; providing vector versions would allow them to be sized arbitrarily large with no reduction of quality.

The SVG images should have the text converted to paths to avoid depending on the fonts for rendering.

[djnavarro]

In principle it's not too difficult to include svg versions. The original version of my code exported everything to svg as well as png, and it is something that I would like to do. I removed the code for that because the svglite package was giving me a little grief. That said, I completely agree that this is a very good idea and I vaguely remember that I used to know how to convert fonts to paths. I'm happy to dig a little deeper and see if I can fix the problem!

[djnavarro]

@ianmcook SVG files now added for everything except the hex stickers. The fonts are all rendered as paths. There are some very subtle differences between the SVG and PNG files, which I think relates to low level graphic driver issues. But the differences are so small that I'm not really bothered about that right now

I'd be happy to merge this version 😁