Currently if sizes is not defined, Next.js is setting sizes as:
```
(max-width: 640px) 640px, (max-width: 750px) 750px, (max-width: 828px) 828px, (max-width: 1080px) 1080px, (max-width: 1200px) 1200px, (max-width: 1920px) 1920px, (max-width: 2048px) 2048px, 3840px'
```
This pull request will make sizes be `100vw` by default, which will allow us to download "smaller" images than what's currently happening.
In a demo app I have, the difference is between downloading 488KB vs 1.4MB (in images)
8340e6d345