WebP support detection

[randolf]

I'm wondering what approach I should use for adding a detection for WebP image format support. I'm thinking that a simple series of internal checks on browser types and minimum version numbers would be the way to go.

Here's a chart of which browser versions support the WebP image format:

https://caniuse.com/#feat=webp

Any suggestions? I'd be happy to write some code for a webp() subroutine that behaves like the mobile() subroutine.

Thanks.

[oalders]

This sounds like a great feature to add. I don't have a lot in the way of suggestions. Following the pattern for mobile() sounds good. We'd just need appropriate tests to accompany the PR. Feel free to ping me if you run into any issues while getting this going.