feat: add empty LaughterFeatureDetector

for jrgillick/laughter-detection to slot into

pipeline/feature_extractors.py

@@ -13,3 +13,18 @@ class FeatureExtractor(ABC):
 
     def teardown(self):
         pass
+class LaughterFeatureExtractor(FeatureExtractor):
+    """Feature extractor for laughter detection.
+
+    This class is responsible for extracting features corresponding to laughter in media files.
+
+    Here:
+
+     setup() is used to validate input files & config, which may involve processing video files to extract audio
+
+     run() is used to extract features from the audio using jrgillick's laughter-detection
+
+     teardown() is used to clean up any temporary files created during setup according to the config
+
+    See: https://github.com/jrgillick/laughter-detection for the laughter-detection library
+    """