Document default values of alignItems and justifyContent (#2733)

Author: nguyenhuy

AsyncDisplayKit/Layout/ASStackLayoutElement.h

@@ -46,13 +46,14 @@ NS_ASSUME_NONNULL_BEGIN
 
 /**
  * @abstract Specifies the initial size in the stack dimension for this object.
- * Default to ASDimensionAuto
+ * Defaults to ASDimensionAuto.
  * Used when attached to a stack layout.
  */
 @property (nonatomic, readwrite) ASDimension flexBasis;
 
 /**
- * @abstract Orientation of the object along cross axis, overriding alignItems
+ * @abstract Orientation of the object along cross axis, overriding alignItems.
+ * Defaults to ASStackLayoutAlignSelfAuto.
  * Used when attached to a stack layout.
  */
 @property (nonatomic, readwrite) ASStackLayoutAlignSelf alignSelf;

AsyncDisplayKit/Layout/ASStackLayoutSpec.h

@@ -55,9 +55,9 @@ NS_ASSUME_NONNULL_BEGIN
  Thus, it is preferred to those properties
  */
 @property (nonatomic, assign) ASVerticalAlignment verticalAlignment;
-/** The amount of space between each child. */
+/** The amount of space between each child. Defaults to ASStackLayoutJustifyContentStart */
 @property (nonatomic, assign) ASStackLayoutJustifyContent justifyContent;
-/** Orientation of children along cross axis */
+/** Orientation of children along cross axis. Defaults to ASStackLayoutAlignItemsStretch */
 @property (nonatomic, assign) ASStackLayoutAlignItems alignItems;
 /** If YES the vertical spacing between two views is measured from the last baseline of the top view to the top of the bottom view */
 @property (nonatomic, assign) BOOL baselineRelativeArrangement;