Force adherence to image guidelines

[httphypixelnet]

Currently, there are many (20) unoptimized PNGs that made it past code review. Two approaches could be taken:

• Enforce a WebP-only rule in the linting pipeline (IE: fail the lint if there are any PNG files in the repo)
• Use sharp to transform the PNGs at build time

[httphypixelnet]

Willing to implement either, if you guys can agree on which approach to take

[samfreund]

I think I'd be okay with enforcing webp only via linting. I'd like some opinions from others prior to implementation tho.