Fix Ruby Podfile code style in docs (#324)

Summary:
2 spaces, and space before and after the `+`
Pull Request resolved: https://github.com/facebook/flipper/pull/324

Reviewed By: jknoxville

Differential Revision: D13082547

Pulled By: priteshrnandgaonkar

fbshipit-source-id: b6053ebde16a1f7f953704e0791622d3d59cc962

docs/getting-started.md

@@ -98,6 +98,7 @@ flipperkit_version = '0.11.1'
 
 target 'MyApp' do
   platform :ios, '9.0'
+
   pod 'FlipperKit', '~>' + flipperkit_version
   # Layout and network plugins are not yet supported for swift projects
   pod 'FlipperKit/FlipperKitLayoutComponentKitSupport', '~>' + flipperkit_version
@@ -105,7 +106,6 @@ target 'MyApp' do
   pod 'FlipperKit/FlipperKitUserDefaultsPlugin', '~>' + flipperkit_version
 
   post_install do |installer|
-
     installer.pods_project.targets.each do |target|
       if ['YogaKit'].include? target.name
         target.build_configurations.each do |config|