IGListDiffKit should support APPLICATION_EXTENSION_API_ONLY (#1422)

Summary:
## Changes in this pull request

Issue fixed: #1421

This PR checks the box that indicates the framework is safe to be used in App Extensions
<img width="302" alt="Screen Shot 2020-02-08 at 3 27 47 PM" src="https://user-images.githubusercontent.com/3067328/74091722-883e1880-4a88-11ea-8ef4-61199704e1ba.png">

### Checklist

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Pull Request resolved: #1422

Differential Revision: D20129657

Pulled By: lorixx

fbshipit-source-id: a39f74b450dcf35adb7d16cd47ee735856d2c728

CHANGELOG.md

@@ -8,6 +8,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Introduce `IGListSwiftKit`, with Swift refinements for `dequeueReusableCellOfClass` methods. [Koen Punt](https://github.com/koenpunt) [(#1388)](https://github.com/Instagram/IGListKit/pull/1388).
 
+- Added `APPLICATION_EXTENSION_API_ONLY` support for `IGListDiffKit` [Peter Meyers](https://github.com/pm-dev) [(#1422)](https://github.com/Instagram/IGListKit/pull/1422)
+
 4.0.0
 -----
 ### Breaking Changes

IGListKit.xcodeproj/project.pbxproj

@@ -2093,6 +2093,7 @@
 		7A02D0232361520200B49FAE /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -2120,6 +2121,7 @@
 		7A02D0242361520200B49FAE /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -2146,6 +2148,7 @@
 		7A02D0312361525800B49FAE /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -2175,6 +2178,7 @@
 		7A02D0322361525800B49FAE /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -2203,6 +2207,7 @@
 		7A02D03E2361526600B49FAE /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_OBJC_WEAK = YES;
@@ -2232,6 +2237,7 @@
 		7A02D03F2361526600B49FAE /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
 				CLANG_ENABLE_OBJC_WEAK = YES;