Update document and comments of gap

Author: Skyline-23

README.md

@@ -679,6 +679,20 @@ This property takes the same values as the width and height properties, and spec
 
 <br>
 
+### gap
+- Applies to: `flex containers`
+- CSS name: `gap`
+
+**Method:**
+
+* **`setGap(_ gutter: Gutter, _value: CGFloat)`**  
+This property set distance between rows and columns. 
+
+* **`getGap(_ gutter: Gutter)`**  
+This property return setted value through `setGap(_ gutter: Gutter, _value: CGFloat)`
+
+<br/>
+
 ### isIncludedInLayout()
 - Applies to: `flex items`
 

Sources/Swift/FlexLayout.swift

@@ -1218,7 +1218,10 @@ public final class Flex {
     //
 
     /**
-     Get paddings between views.
+     Get setted value through func `setGap(_ gutter: Gutter, _ value: CGFloat)`.
+     
+     - Parameter gutter: directions
+     - Returns: distance
     */
     @discardableResult
     public func getGap(_ gutter: Gutter) -> CGFloat {
@@ -1230,7 +1233,12 @@ public final class Flex {
     }
 
     /**
-     Set paddings between views.
+     Set distance between rows and columns.
+     
+     - Parameters:
+       - gutter: directions
+       - value: distance
+     - Returns: flex interface
     */
     @discardableResult
     public func setGap(_ gutter: Gutter, _ value: CGFloat) -> Flex {