Percent encode curly braces

[valenting]

According to https://bugzilla.mozilla.org/show_bug.cgi?id=1152455#c6 most UAs encode curly braces in the path of the URL.
I think rust-url should do the same.

[SimonSapin]

The spec says it must not: https://url.spec.whatwg.org/#percent-encoded-bytes . If the spec is wrong, an issue should be filed on it and discussed before we unilaterally start deviating. (See "Participate" near the top of the spec, and feel free to @-mention me in spec issues.)

[valenting]

whatwg/url#16

[valenting]

The spec has been changed: whatwg/url#16

[SimonSapin]

The spec added { and } to the "default encode set". I’d prefer doing that as well rather than some other change, even if the black-box behaviour happens to be identical (which I’m not convinced it is).

[valenting]

Right, that sounds fair. I'm closing this PR. Let me know if you want me to submit another, or if it's faster to change it yourself.
Thanks!

[SimonSapin]

Done in 79a9ef1