Added option for creating custom resolutions

[MaurilhoB]

Added an option for users to create their own custom resolutions in the desired aspect ratio. If the user has a phone with a 20:9 aspect ratio and a resolution of 2400x1080, they could scale it down to 1920x864 and still have full screen utilization.

I had this problem with my native resolution not being supported by the decoder, so I made this adjustment to enable full screen utilization simply by downscaling the resolution.

[quangmach]

Please merge this to master. This custom resolution has been requested for few years already. Thank you!

[zhoumother]

太感谢了

[kajdo]

I would love to see this becoming part of the official repo