add README.md with iOS implementation info

Author: Ivan Dlugos

ios/README.md

@@ -0,0 +1,16 @@
+Contents of this folder is based on `flutter create --template=plugin`.
+It was reduced to the minimum that works for library inclusion by client apps.
+
+Notably, the package depends on `ObjectBox.framework` from ObjectBox Swift distribution, downloading
+a released `ObjectBox-framework-X.Y.Z.zip` archive. 
+
+## Current limitations/TODOs
+There's currently an [issue](https://github.com/flutter/flutter/issues/45778) with Flutter tooling and/or its integration 
+with Cocoapods. In short, an "http" source in the podspec doesn't work - the file has to be available locally.
+ 
+To circumvent this, we're currently including the extracted `ObjectBox.framework` for iOS in the package when publishing 
+to pub.dev. Therefore, you need to run ./ios/download-framework.sh before publishing the package.
+This has the benefit of a "no-setup" iOS support for the ObjectBox users - it works out of the box.
+Also notably, we're only including the bare minimum from the ObjectBox Swift release which means smaller final app size.    
+ 
+Note for contributors: you need to run the above-mentioned script as well to be able to test ObjectBox on iOS.

ios/objectbox.podspec

@@ -12,12 +12,7 @@ Pod::Spec.new do |s|
   s.author           = 'ObjectBox'
   s.platform         = :ios, '8.0'
 
-  # Get the ObjectBox.framework from the objectbox-swift release
-  # TODO: getting from http currently doesn't work - see https://github.com/flutter/flutter/issues/45778
-  # To circumvent this, we're currently including the extracted framework in the package when publishing to pub.dev
-  # Therefore, you need to run ./ios/download-framework.sh before publishing the package (or if you're working on
-  # ObjectBox-Dart as a developer and need to test it for iOS)
-  # s.source = { :http => 'https://github.com/objectbox/objectbox-swift/releases/download/v1.2.0/ObjectBox-framework-1.2.0.zip' }
+  # Get the ObjectBox.framework from the objectbox-swift release (see README.md)
   s.source = { :path => '.' }
 
   s.ios.vendored_frameworks = 'Carthage/Build/iOS/ObjectBox.framework'