Write missing docs and reenable deny statements

native/src/renderer/null.rs

@@ -11,6 +11,9 @@ use crate::{
 pub struct Null;
 
 impl Null {
+    /// Creates a new [`Null`] renderer.
+    ///
+    /// [`Null`]: struct.Null.html
     pub fn new() -> Null {
         Null
     }

native/src/renderer/windowed.rs

@@ -4,6 +4,7 @@ use raw_window_handle::HasRawWindowHandle;
 
 /// A renderer that can target windows.
 pub trait Windowed: super::Renderer + Sized {
+    /// The settings of the renderer.
     type Settings: Default;
 
     /// The type of target.