add docs

doc/function/index.txt

@@ -86,6 +86,7 @@ These functions are built into the program, other [[type:function]]s can be defi
 | [[fun:saturate]]		Saturate/desaturate an image.
 | [[fun:invert_image]]		Invert the colors of an image.
 | [[fun:recolor_image]]		Change the colors of an image to match the font color.
+| [[fun:resize_image]]		Stretch or squeeze an image to a given height and width.
 | [[fun:enlarge]]		Enlarge an image by putting a border around it.
 | [[fun:crop]]			Crop an image, giving only a small subset of it.
 | [[fun:flip_horizontal]]	Flip an image horizontally.

doc/function/resize_image.txt

@@ -0,0 +1,14 @@
+Function: resize_image
+
+--Usage--
+> resize_image(input: image, height: height_of_new_image, width: width_of_new_image)
+
+Shrink or grow an image to a new size specified in the parameters, so it can be further worked on.
+If you want to display an image in a field, MSE will automatically resize it to fit the field, you do not need to use this function.
+
+--Parameters--
+! Parameter		Type				Description
+| @input@		[[type:image]]		Image to resize
+| @height@		[[type:int]]		Height of the resulting image
+| @width@		[[type:int]]		Width of the resulting image
+