Added missing documentation for image and fliptype

Author: not-phoeniix

api/fliptype.md

@@ -1,5 +1,12 @@
 # FlipType
 
+Type of flipping to be used in [image:flip](image.md#imageflip)
+
 ## FlipType.HORIZONTAL
+Defines a type of image flip that horizontally flips an image across the vertical axis.
 
 ## FlipType.VERTICAL
+Defines a type of image flip that vertically flips an image across the horizontal axis.
+
+## FlipType.DIAGONAL
+Defines a type of image flip that both vertically and horizontally flips an image across the diagonal axis.

api/image.md

@@ -82,12 +82,16 @@ are modified).
 local w = image.width
 ```
 
+Returns the width of the image in pixels.
+
 ## Image.height
 
 ```lua
 local h = image.height
 ```
 
+Returns the height of the image in pixels.
+
 ## Image.bounds
 
 ```lua
@@ -337,3 +341,12 @@ local rectangle = image:shrinkBounds(refColor)
 Returns the shrunken bounds (a [rectangle](rectangle.md#rectangle)) of
 the image removing all the empty space of borders using the mask color
 or the given reference [color](color.md#color) in `refColor`.
+
+## Image:flip()
+
+```lua
+image:flip()
+image:flip(FlipType.VERTICAL)
+```
+
+Flips an image along an axis defined by a [FlipType](fliptype.md). Flips horizontally if [FlipType](fliptype.md) is not specified by default.