Inter-crate links are broken on docs.rs

[andyleiserson]

There are a bunch of links from hal, core, and types to wgpu documentation written like this:

wgpu/wgpu-types/src/lib.rs

Line 101 in 1791064

/// [`map_async()`]: ../wgpu/struct.Buffer.html#method.map_async

I assume this works when the documentation is built and viewed locally. But on docs.rs, the relative link resolves to https://docs.rs/wgpu-types/latest/wgpu/struct.Buffer.html#method.map_async, which does not exist.