Add Experimental Text Node Implementation (#259)

* Add experimental text node implementation, based on YYText

* Fix warnings and alert when unimplemented experimental features are used.

* Address feedback from review

* Extend the cthulog

* Update license headers

Source/Private/TextExperiment/Utility/NSParagraphStyle+ASText.h

@@ -0,0 +1,37 @@
+//
+//  NSParagraphStyle+ASText.h
+//  Modified from YYText <https://github.com/ibireme/YYText>
+//
+//  Created by ibireme on 14/10/7.
+//  Copyright (c) 2015 ibireme.
+//
+//  This source code is licensed under the MIT-style license found in the
+//  LICENSE file in the root directory of this source tree.
+//
+
+#import <UIKit/UIKit.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ Provides extensions for `NSParagraphStyle` to work with CoreText.
+ */
+@interface NSParagraphStyle (ASText)
+
+/**
+ Creates a new NSParagraphStyle object from the CoreText Style.
+ 
+ @param CTStyle CoreText Paragraph Style.
+ 
+ @return a new NSParagraphStyle
+ */
++ (nullable NSParagraphStyle *)as_styleWithCTStyle:(CTParagraphStyleRef)CTStyle;
+
+/**
+ Creates and returns a CoreText Paragraph Style. (need call CFRelease() after used)
+ */
+- (nullable CTParagraphStyleRef)as_CTStyle CF_RETURNS_RETAINED;
+
+@end
+
+NS_ASSUME_NONNULL_END