Set name of unnamed threads

src/main/java/eu/crushedpixel/replaymod/video/ReplayScreenshot.java

@@ -96,7 +96,7 @@ public class ReplayScreenshot {
                         TickAndRenderListener.finishScreenshot();
                     }
                 }
-            });
+            }, "replaymod-screenshot-saver");
 
             ioThread.start();
         } catch(Exception exception) {

src/main/java/eu/crushedpixel/replaymod/video/VideoWriter.java

@@ -110,7 +110,7 @@ public class VideoWriter {
                     e.printStackTrace();
                 }
             }
-        });
+        }, "replaymod-video-writer");
         writerThread.start();
     }