chore(docs): fix typeo in README

Closes #4677

Author: claushellsing

README.md

@@ -36,7 +36,7 @@ Are you interested in Angular 2? We are on our way! Check out [ng-bootstrap](htt
 Installation is easy as UI Bootstrap has minimal dependencies - only the AngularJS and Twitter Bootstrap's CSS are required.
 Note: Since version 0.13.0, UI Bootstrap depends on [ngAnimate](https://docs.angularjs.org/api/ngAnimate) for transitions and animations, such as the accordion, carousel, etc. Include `ngAnimate` in the module dependencies for your app in order to enable animation.
 
-Additionally, it is srongly recommended that for UI Bootstrap 0.13.3 and higher you use Angular 1.3.18 or higher due to animation fixes.
+Additionally, it is strongly recommended that for UI Bootstrap 0.13.3 and higher you use Angular 1.3.18 or higher due to animation fixes.
 
 #### Install with NPM