Transfer gallery to official documentation

[lazarusA]

Hi, I was wondering if you would be open to transfer the gallery https://lazarusa.github.io/gnuplot-examples/ into this section https://gcalderone.github.io/Gnuplot.jl/stable/examples/ in the official documentation? Plus, use the same style. If so, I could prepare a PR.

Best, Lazaro

[gcalderone]

Yes, this is a good idea, thank you! Please ensure you keep the proper credit for your contribution ;-)