Allow Matroska clusters that don't begin with a key frame

src/media-source.ts

@@ -264,7 +264,7 @@ class VideoEncoderWrapper {
 
 		// Ensure a key frame every keyFrameInterval seconds. It is important that all video tracks follow the same
 		// "key frame" rhythm, because aligned key frames are required to start new fragments in ISOBMFF or clusters
-		// in Matroska.
+		// in Matroska (or at least desirable).
 		const finalEncodeOptions = {
 			...encodeOptions,
 			keyFrame: encodeOptions?.keyFrame