Fix dash download (#2258x2)

* Update docs with root_url to properly allow Dash downloads.

* Commit missing logo image and regenerate.

* Add trailing slash to fix Dash again.

.jazzy.yaml

@@ -1,7 +1,7 @@
 author: Alamofire Software Foundation
 author_url: http://alamofire.org/
 github_url: https://github.com/Alamofire/Alamofire
-root_url: https://alamofire.github.io/Alamofire
+root_url: https://alamofire.github.io/Alamofire/
 module: Alamofire
 output: docs
 theme: fullwidth