Add support for Gopro .360 format

[fisheggg]

This PR adds support for the special .360 format used by GoPro MAX. By add the submodule made by Alexander (https://github.com/alexarje/gopromax-conversion-tools), the Mg360Video is now able to init with projection="gopro_360", and convert it to either equirectangular or dual fisheye format. An example would be:

video = Mg360Video('path/to/video.360', projection="gopro_360")
video.convert_projection(
    target_projection = Projection.equirect, # or Projection.dfisheye
    options={"-r": "0:180:0"}, # optional flags, gives 180 degs of yaw when converting
)

After being converted to equirect, it can be further converted to other projections using the previous functions in Mg360Video by calling the ffmpeg vfilter options.

I've tested the equirect conversion that seems to work well, but there seems to be some issues with the dual fisheye conversion. Nevertheless, I assume the API can be the same and therefore I've included both functionalities. It can be fixed by updating the submodule once the conversion script is fixed.

Another small issue is that the projection conversion is really slow, I got ~x0.15 speed comparing to realtime.

Finally, I wanted to add 360 related contents to the MGT wiki, but it seems like that I need some extra permissions to change the wiki contents. Can anyone help me with that? Thanks in advance :)

Best,
Arthur