doc: Document the behavior when mis-configuring width/height of Surface

wgpu-types/src/lib.rs

@@ -5530,8 +5530,18 @@ pub struct SurfaceConfiguration<V> {
  /// `Bgra8Unorm` and `Bgra8UnormSrgb`
  pub format: TextureFormat,
  /// Width of the swap chain. Must be the same size as the surface, and nonzero.
+ ///
+ /// If this is not the same size as the underlying surface (e.g. if it is
+ /// set once, and the window is later resized), the behaviour is defined
+ /// but platform-specific, and may change in the future (currently macOS
+ /// scales the surface, other platforms may do something else).
  pub width: u32,
  /// Height of the swap chain. Must be the same size as the surface, and nonzero.
+ ///
+ /// If this is not the same size as the underlying surface (e.g. if it is
+ /// set once, and the window is later resized), the behaviour is defined
+ /// but platform-specific, and may change in the future (currently macOS
+ /// scales the surface, other platforms may do something else).
  pub height: u32,
  /// Presentation mode of the swap chain. Fifo is the only mode guaranteed to be supported.
  /// FifoRelaxed, Immediate, and Mailbox will crash if unsupported, while AutoVsync and