Initial VegaLite support

[pablosanjose]

If using VegaLite, this adds a method vlplot(b::Bandstructure{1}; kw...) for super-fast, beautiful and interactive plotting of 1D bandstructures in your browser. Can also export as a vector pdf/svg/etc...

Example:

julia> using Quantica, VegaLite

julia> h = LatticePresets.square() |> hamiltonian(hopping(1)) |> unitcell(8);

julia> mesh1D = marchingmesh(range(0,2π,length=81));

julia> b = bandstructure(h, mesh1D, cut = φ -> (φ, -φ))
Step 1/2 - Diagonalising: 100%|█████████| Time: 0:00:00
Bandstructure{1}: collection of 1D bands
  Bands        : 60
  Element type : scalar (Complex{Float64})
  Mesh{1}: mesh of a 1-dimensional manifold
    Vertices   : 81
    Edges      : 80

julia> vlplot(b; points = true)

PS: VegaLite is amazing