Animated WebP support (#5470)

Adds support for animated WebP images. Used the already existing GIF
implementation as a template for most of it.

* [x] I have followed the instructions in the PR template

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

Cargo.lock

@@ -2202,12 +2202,23 @@ dependencies = [
  "byteorder-lite",
  "color_quant",
  "gif",
+ "image-webp",
  "num-traits",
  "png",
  "zune-core",
  "zune-jpeg",
 ]
 
+[[package]]
+name = "image-webp"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e031e8e3d94711a9ccb5d6ea357439ef3dcbed361798bd4071dc4d9793fbe22f"
+dependencies = [
+ "byteorder-lite",
+ "quick-error",
+]
+
 [[package]]
 name = "images"
 version = "0.1.0"
@@ -3165,6 +3176,12 @@ dependencies = [
  "puffin_http",
 ]
 
+[[package]]
+name = "quick-error"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a993555f31e5a609f617c12db6250dedcac1b0a85076912c436e6fc9b2c8e6a3"
+
 [[package]]
 name = "quick-xml"
 version = "0.30.0"