Resolution subsampler passes through metadata (#273)

Co-authored-by: iejMac <[email protected]>

video2dataset/subsamplers/resolution_subsampler.py

@@ -46,4 +46,4 @@ def __call__(self, streams, metadata=None):
                 with open(f"{tmpdir}/output.mp4", "rb") as f:
                     subsampled_bytes.append(f.read())
         streams["video"] = subsampled_bytes
-        return streams, None, None
+        return streams, metadata, None