Switch from Gtk to GLFW

[kraftpunk97-zz]

[anandijain]

Would change up the render!(env), to allow for running julia scripts from terminal and display the video?

Currently, w/o being in an IJulia notebook, the output of demo_script from readme and render!(env) is just:

$ julia basic_diffrl.jl                       
Cairo.CairoSurfaceBase{UInt32}(Ptr{Nothing} @0x0000000014b86890, 600.0, 400.0)
...
Cairo.CairoSurfaceBase{UInt32}(Ptr{Nothing} @0x0000000014b86890, 600.0, 400.0)

Currently, is there a way to render!() from terminal?