Write documentation for new iced_wgpu types

wgpu/src/window/backend.rs

@@ -3,6 +3,7 @@ use crate::{window::SwapChain, Renderer, Settings, Target};
 use iced_native::MouseCursor;
 use raw_window_handle::HasRawWindowHandle;
 
+/// A window graphics backend for iced powered by `wgpu`.
 #[derive(Debug)]
 pub struct Backend {
     device: wgpu::Device,

wgpu/src/window/swap_chain.rs

@@ -12,6 +12,9 @@ pub struct SwapChain {
 impl SwapChain {}
 
 impl SwapChain {
+    /// Creates a new [`SwapChain`] for the given surface.
+    ///
+    /// [`SwapChain`]: struct.SwapChain.html
     pub fn new(
         device: &wgpu::Device,
         surface: &wgpu::Surface,
@@ -24,6 +27,10 @@ impl SwapChain {
         }
     }
 
+    /// Returns the next frame of the [`SwapChain`] alongside its [`Viewport`].
+    ///
+    /// [`SwapChain`]: struct.SwapChain.html
+    /// [`Viewport`]: ../struct.Viewport.html
     pub fn next_frame(&mut self) -> (wgpu::SwapChainOutput<'_>, &Viewport) {
         (self.raw.get_next_texture(), &self.viewport)
     }