Fix the following issue:

I want the `manimgl` and `manim-render` commands to support opening or revealing rendered output files directly from the CLI. When I run `manimgl path/to/scene.py SceneName --open` or `manimgl path/to/scene.py SceneName -o`, the command should render the scene to a media file just like `--write_file`, and after the movie or final-frame image has been saved it should launch that saved file with the platform's default opener. Passing `--open` by itself should imply file writing; users should not also have to pass `--write_file`.

I also want `manimgl path/to/scene.py SceneName --finder` to imply file writing and then reveal the saved output in the operating system's file browser when rendering completes. If the run saves only the final frame with `--skip_animations`, the image file should be opened or revealed; otherwise the movie file should be opened or revealed. These flags should appear in `manimgl --help` with `-o, --open` described as automatically opening the saved file and `--finder` described as showing the output file in Finder/file browser. A successful render that opens or reveals the output should still exit with code 0.