Fix various typos and grammar nits

I also removed all trailing whitespace from lines since I have Emacs
configured to highlight this.

packages/mobile/README.md

@@ -21,7 +21,7 @@ $ cargo install --git https://github.com/BrainiumLLC/cargo-mobile
 And then initialize your app for the right platform. Use the `winit` template for now. Right now, there's no "Dioxus" template in cargo-mobile.
 
 ```shell
-$ cargo mobile init 
+$ cargo mobile init
 ```
 
 We're going to completely clear out the `dependencies` it generates for us, swapping out `winit` with `dioxus-mobile`.