Wiki update for blending mode specifier change (#10429) (#45)

wiki/BlendingModes.md

@@ -77,7 +77,7 @@ That is, we're adding somewhere between 50% and 100% of the background to the ob
 
 One problem with all of this: depending on your graphics program, it can be really hard to save a PNG files where all the alpha values are zero, and yet the color values are perfectly preserved. What's more, even if you are able to save such a file, opening it in most image viewers will show you a transparent image, rather than the colors that you want to see.
 
-For this reason, Endless Sky is designed to do the premultiplication after loading the image, based on the image name. Each image can (optionally) include a blending mode specifier right before the frame index number: `-` for alpha blending, `+` for additive blending, or `~` for half-additive blending. When each image is read, the alpha premultiplication is done, and then the alpha channel is set to 0 if it is an additive image, or divided by 2 if it is half-additive. This makes it very easy to create input images without any special software tools.
+For this reason, Endless Sky is designed to do the premultiplication after loading the image, based on the image name. Each image can (optionally) include a blending mode specifier right before the frame index number: `-` for alpha blending, `+` for additive blending, or `^` for half-additive blending. (Before **v0.10.9**, half-additive blending used `~`, but that is now deprecated.) When each image is read, the alpha premultiplication is done, and then the alpha channel is set to 0 if it is an additive image, or divided by 2 if it is half-additive. This makes it very easy to create input images without any special software tools.
 
 For images that are drawn in additive mode, you can supply them as a completely opaque image drawn over a black background. Or, you can just supply an image with transparency, and the additive image will be generated by adding a black background to the image.