add ffmpeg in rtd

Author: skim0119

.readthedocs.yaml

@@ -4,6 +4,8 @@ version: 2
 # Set the version of Python and other tools you might need
 build:
   os: ubuntu-24.04
+  apt_packages:
+    - ffmpeg
   tools: { python: "3.10" }
   jobs:
     create_environment:
@@ -14,6 +16,7 @@ build:
     install:
       - "true"
 
+
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
   builder: html