Improve sponsor promotion

[mattstein]

#44 implied that we could be doing a better job of promoting project sponsors and acknowledging various levels of commitment.

I propose we do the following:

• Create/generate a .svg image to embed in the ddev/ddev readme, so we can consistently use high-quality logos from the same source and fix abhorrent spacing issues that aren’t kind to any of them.
• Visually emphasize top-level sponsors on the ddev.com homepage, and possibly do the same thing with the readme.
• Again promote top-level sponsors globally in ddev.com’s footer, which has a lot of room for it.
• Identify any other opportunities within repositories, ddev.com, the docs, etc. that might tastefully promote sponsors without getting in the way of whatever the user/reader is doing.

Whatever “top-level” means, we should also update the GitHub sponsors page to reflect a clear policy for this so it’s fair and always apparent where sponsor logos need to go.

[rfay]

Sounds great to me!

[rfay]

I think this one is all sorted out. There's probably more we can do, can follow up in

• Add key sponsors (GitHub or not) to support page #44

[rfay]

Thanks for the amazing work on this @mattstein !