Additional AVIF options (#987)

* Separate colour & alpha options for AVIF

* Adding broken noise synthesis

* Build files

* Updating build

* Changing speed default

* Remove old comment

* Better speed default

codecs/avif/enc/avif_enc.d.ts

@@ -1,6 +1,7 @@
 export interface EncodeOptions {
   cqLevel: number;
-  minQuantizerAlpha: number;
+  denoiseLevel: number;
+  cqAlphaLevel: number;
   tileRowsLog2: number;
   tileColsLog2: number;
   speed: number;