Changed project to APPLICATION_EXTENSION_API_ONLY = YES (#353)

The framework still builds and tests still pass, so I think this is better to ensure that the library continues to work with the more restrictive option.
This is a follow up to #352 and #351.

Author: NachoSoto

SnapshotTesting.xcodeproj/project.pbxproj

@@ -950,6 +950,7 @@
 		0599123409D3A74965DD7DF5 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				INFOPLIST_FILE = Tests/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = (
@@ -968,6 +969,7 @@
 		2277B56067B75046C0A1B62F /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				INFOPLIST_FILE = Tests/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = (
@@ -986,6 +988,7 @@
 		40A5D28387BCBCA2CC1FE11C /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				INFOPLIST_FILE = Tests/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = (
@@ -1004,6 +1007,7 @@
 		4FA7607F66B8ABA649B6056C /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CODE_SIGN_IDENTITY = "";
 				COMBINE_HIDPI_IMAGES = YES;
 				CURRENT_PROJECT_VERSION = 1;
@@ -1031,6 +1035,7 @@
 		7A892D3CF9DFA14F5D83DDC6 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				COMBINE_HIDPI_IMAGES = YES;
 				INFOPLIST_FILE = Tests/Info.plist;
@@ -1049,6 +1054,7 @@
 		97BC453D0A2FD987C257005F /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CODE_SIGN_IDENTITY = "";
 				COMBINE_HIDPI_IMAGES = YES;
 				CURRENT_PROJECT_VERSION = 1;
@@ -1129,6 +1135,7 @@
 		CF766E2537E4426A0D7C2694 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CODE_SIGN_IDENTITY = "";
 				CURRENT_PROJECT_VERSION = 1;
 				DEFINES_MODULE = YES;
@@ -1156,6 +1163,7 @@
 		D9FF7D396CC20A3E59EB1145 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CODE_SIGN_IDENTITY = "";
 				CURRENT_PROJECT_VERSION = 1;
 				DEFINES_MODULE = YES;
@@ -1183,6 +1191,7 @@
 		DE96DD966ECF6C6107DC8979 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CODE_SIGN_IDENTITY = "";
 				CURRENT_PROJECT_VERSION = 1;
 				DEFINES_MODULE = YES;
@@ -1271,6 +1280,7 @@
 		EE2EEFC9F90E51027AEC6732 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				INFOPLIST_FILE = Tests/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = (
@@ -1289,6 +1299,7 @@
 		F5C56FCFB9CA36D38912B3F7 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CODE_SIGN_IDENTITY = "";
 				CURRENT_PROJECT_VERSION = 1;
 				DEFINES_MODULE = YES;
@@ -1316,6 +1327,7 @@
 		FFBA36D8171A8AF1E78CE7BE /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				COMBINE_HIDPI_IMAGES = YES;
 				INFOPLIST_FILE = Tests/Info.plist;

project.yml

@@ -15,6 +15,7 @@ targets:
       ENABLE_BITCODE: false
       FRAMEWORK_SEARCH_PATHS: $(inherited) $(PLATFORM_DIR)/Developer/Library/Frameworks
       SWIFT_VERSION: 5.0
+      APPLICATION_EXTENSION_API_ONLY: 'YES'
     scheme:
       environmentVariables:
         SNAPSHOT_ARTIFACTS: /tmp/__SnapshotArtifacts__
@@ -26,6 +27,7 @@ targets:
     platform: [macOS, iOS, tvOS]
     settings:
       SWIFT_VERSION: 5.0
+      APPLICATION_EXTENSION_API_ONLY: 'YES'
     sources:
       - path: Tests
         excludes: