Fix documentation deployment

[j-fu]

I guess we should deploy to https://JuliaPluto.github.io/PlutoStaticHTML
instead of http://plutostatichtml.huijzer.xyz/ .

[rikhuijzer]

Yes. Good idea

[rikhuijzer]

Let me know if I should do it or can review something. (I won't be quick because of a new job, but I'll get there.)