Memory leak

**Describe the bug**
After encoding a video with ffmpeg.run(), the memory allocation increases but will never be released. Even with ffmpeg.exit() nothing changes (I stored the .png files in the virtual FS and then I've removed them after the video encoding was done).

**To Reproduce**
Encode a video using images stored in virtual file system. I've used the command:

`ffmpeg.run('-framerate', '60', '-i', 'input%d.png', '-crf', '18', '-c:v', 'libx264', '-pix_fmt', 'yuv420p', 'output.mp4');`

You can watch the memory grow in the Task Manager over and over, never going back significantly. I've also tried running the garbage collector from Chrome, but it doesn't change anything.

**Expected behavior**
The memory must be released at the end of the encoding.

**Desktop (please complete the following information):**
- OS: Windows 10 Pro
- Browser: Chrome
- Version: 113