Yarn uses add not install (react-navigation#203)

Shaun Stanworth · vonovak · commit 11b98ed57721 · 2018-06-25T18:11:41.000+02:00
diff --git a/docs/community-fluidtransitions.md b/docs/community-fluidtransitions.md
@@ -16,7 +16,7 @@ Install the FluidTransitions package in your project:
 
 ```
 npm install react-navigation-fluid-transitions
-yarn install  react-navigation-fluid-transitions
+yarn add react-navigation-fluid-transitions
 ```
 
 ## Links
