Improve ayu rustdoc theme
Improve ayu rustdoc theme

* It makes some lines darker
* It gives the crate selector and search bar a border
  * The search bar's border turns blue when focused
* Gives the logo a bright shadow. This makes dark logos stand out more
aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust