Fix navigation links in documentation.

Summary:
When navigating in the docs, these two links are broken.

The "Continue Reading" in http://facebook.github.io/react-native/docs/more-resources.html page, and "Previous" in http://facebook.github.io/react-native/docs/platform-specific-code.html.

This PR is to fix this.
Closes https://github.com/facebook/react-native/pull/16236

Differential Revision: D5998970

Pulled By: hramos

fbshipit-source-id: b339408eaada612133f6b63bd11967196ff3a039

docs/ComponentsAndAPIs.md

@@ -1,5 +1,5 @@
 ---
-id: components
+id: components-and-apis
 title: Components and APIs
 layout: docs
 category: Guides

docs/MoreResources.md

@@ -4,7 +4,7 @@ title: More Resources
 layout: docs
 category: The Basics
 permalink: docs/more-resources.html
-next: components
+next: components-and-apis
 previous: network
 ---
 

docs/PlatformSpecificInformation.md

@@ -5,7 +5,7 @@ layout: docs
 category: Guides
 permalink: docs/platform-specific-code.html
 next: navigation
-previous: components
+previous: components-and-apis
 ---
 
 When building a cross-platform app, you'll want to re-use as much code as possible. Scenarios may arise where it makes sense for the code to be different, for example you may want to implement separate visual components for iOS and Android.