Add support for WEBP images

[matthew-petrie]

Add support for .jpeg.webp & .jpg.webp images in the getSizedImageUrl function.

Shopify outputs images in WEBP format which need to be able to have sizes added, for example this real Shopify URL: https://cdn.shopify.com/s/files/1/0896/0640/products/IMG_20190622_130045_clipped_rev_1.jpeg.webp?v=1582896583

[SpurIT]

Hello,

I am out of the office till March 1. Please reach out to the Sales Manager that you are working with or to [email protected] if you have any questions.

[matthew-petrie]

I've signed the CLA but not sure how to re-run the check

[joshistoast]

Would love to boost our performance with webp images, but the lack of support and this dangling pr is frankly sad