Fix VideoToolbox object memory leak (#5)

Author: saltpi

Sources/Transcoding/VideoDecoder.swift

@@ -23,6 +23,12 @@ public final class VideoDecoder {
         }
         #endif
     }
+    
+    deinit {
+        if let decompressionSession = decompressionSession {
+            VTDecompressionSessionInvalidate(decompressionSession)
+        }
+    }
 
     // MARK: Public
 

Sources/Transcoding/VideoEncoder.swift

@@ -23,6 +23,12 @@ public final class VideoEncoder {
         }
         #endif
     }
+    
+    deinit {
+        if let compressionSession = compressionSession {
+            VTCompressionSessionInvalidate(compressionSession)
+        }
+    }
 
     // MARK: Public