Regarding license of 3DS Dear ImGui integration files

[alvinhochun]

Hi, first of all thanks for making ftpd. It had been extremely helpful throughout the years of 3DS homebrew.

Is your feature request related to a problem? Please describe.
I found out that the 3DS Dear ImGui integration in ftpd is quite standalone and so I have started using it in a project. However there is an oddity - while the main source files (imgui_citro3d / imgui_ctru) has the MIT license header, the shader source (vshader.v.pica) has a GPLv3 license header. While the shader seems trivial to reimplement (and GPL is not an issue in my case), this is still a weird combination.

Describe the solution you'd like
It would make things simpler if vshader.v.pica is also licensed in MIT.

Describe alternatives you've considered
n/a

Additional context
n/a