BREAKING CHANGE:
Using the built-in image optimization API, the URL is parsed with `new
URL()` constructor which automatically trims spaces.
However, the developer may choose a 3rd party image optimization API via
`loader` or `loaderFile` (or perhaps a deployment platform that has its
own built in loader), so we shouldn't assume the API will parse the URL
in the same way as
[WHATWG](https://url.spec.whatwg.org/#:~:text=If%20input%20contains%20any%20leading%20or%20trailing%20C0%20control%20or%20space%2C%20invalid%2DURL%2Dunit%20validation%20error.).
While we could trim on the client, its probably best to fail fast and
let the developer make a conscience decision if a trailing space should
be removed or remain (by explicitly using `%20`).
f169b08901