Basic CocoaPods Validation (#1303)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1303

This gets `pod lib lint` and building the sample app with xcbuild passing (using https://github.com/facebook/yoga/pull/1105 as a template).

Differential Revision: D46470738

fbshipit-source-id: f61eb44c533e1a5fd8c2df0807e2cfd80418406d

YogaKit/YogaKitSample/Podfile

@@ -1,6 +1,17 @@
 use_frameworks!
 
+platform :ios, "13.4"
+
 target 'YogaKitSample' do
   pod 'YogaKit', :path => '../../YogaKit.podspec'
-  pod 'IGListKit', '~> 2.1.0'
+  pod 'Yoga', :path => '../../Yoga.podspec'
+  pod 'IGListKit', '~> 4.0.0'
+end
+
+post_install do |installer|
+  installer.pods_project.targets.each do |target|
+    target.build_configurations.each do |config|
+      config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '13.4'
+    end
+  end
 end