Utilize the cover image for desktop screens and the thumbnail image for mobile screens as the cover image for a course.

[irajsuhail]

Is your feature request related to a problem? Please describe.
The current method of handling cover images for courses across various screens (mobile and desktop) includes resizing the aspect ratio of the image and automatically cropping it for a precise fit. However, this approach presents a couple of challenges:

1. The images may not appear as visually appealing as intended because they are primarily designed for desktop screens.
2. If the cover image designer overlooks the safe area guidelines, the image might be cropped awkwardly.

Describe the solution you'd like
Since we already have multiple images for a course, cover and thumbnail images. Utilize the cover image for desktop screens and the thumbnail image for mobile screens as the cover image for a course.

Additional context
For the school cover image, we should avoid using different aspect ratios for different screens and instead preserve the actual aspect ratio to prevent awkward cropping.