[FEATURE REQUEST] Different wallpapers for permanent workspaces

[iamkartiknayak]

It would be highly beneficial to have the ability to set different wallpapers for each workspace in the Cosmic desktop environment, similar to how workspace-specific tiling layouts are handled. This feature would enhance user experience by allowing greater personalization and could help users visually differentiate between workspaces, thereby improving productivity and organization.

• When frost effect is added in the future, with wallpaper color it could greatly improve UI aesthetics.

See related issue: #513