Merge pull request #25608 from sturkmen72:animated_webp_support

Animated WebP Support #25608

related issues #24855 #22569 

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

cmake/OpenCVFindWebP.cmake

@@ -10,8 +10,6 @@
 
 # Look for the header file.
 
-unset(WEBP_FOUND)
-
 FIND_PATH(WEBP_INCLUDE_DIR NAMES webp/decode.h)
 
 if(NOT WEBP_INCLUDE_DIR)
@@ -21,13 +19,14 @@ else()
 
     # Look for the library.
     FIND_LIBRARY(WEBP_LIBRARY NAMES webp)
-    MARK_AS_ADVANCED(WEBP_LIBRARY)
+    FIND_LIBRARY(WEBP_MUX_LIBRARY NAMES webpmux)
+    FIND_LIBRARY(WEBP_DEMUX_LIBRARY NAMES webpdemux)
 
     # handle the QUIETLY and REQUIRED arguments and set WEBP_FOUND to TRUE if
     # all listed variables are TRUE
     INCLUDE(${CMAKE_ROOT}/Modules/FindPackageHandleStandardArgs.cmake)
     FIND_PACKAGE_HANDLE_STANDARD_ARGS(WebP DEFAULT_MSG WEBP_LIBRARY WEBP_INCLUDE_DIR)
 
-    SET(WEBP_LIBRARIES ${WEBP_LIBRARY})
+    SET(WEBP_LIBRARIES ${WEBP_LIBRARY} ${WEBP_MUX_LIBRARY} ${WEBP_DEMUX_LIBRARY})
     SET(WEBP_INCLUDE_DIRS ${WEBP_INCLUDE_DIR})
 endif()