Update PSPDFKit for iOS required version in the README and cocoapods

Author: RadAzzouz

README.md

@@ -25,7 +25,7 @@ The [PSPDFKit SDK](https://pspdfkit.com/) is a framework that allows you to view
 #### Requirements
 
 - Xcode 10.1
-- PSPDFKit 8.1 for iOS or later
+- PSPDFKit 8.1.3 for iOS or later
 - react-native >= 0.55.4
 
 #### Getting Started

ios/cocoapods.md

@@ -3,8 +3,8 @@
 ### CocoaPods integration
 
 #### Requirements
-- Xcode 10
-- PSPDFKit 8.0 for iOS or later
+- Xcode 10.1
+- PSPDFKit 8.1.3 for iOS or later
 - react-native >= 0.55.4
 - CocoaPods >= 1.5.3