Add ascii and append kwargs to writevtk interface

[pmartorell]

Added ascii = false, append = ! ascii Bool kwargs to writevtk.

The defaults are set according to WriteVTK.jl manual:

https://jipolanco.github.io/WriteVTK.jl/v1.16/grids/syntax/

As ascii is not compatible with append the default append is set to ! ascii

[fverdugo]

Hi @pmartorell

thanks for this.

Up to know the options we were (implicitly) using were ascii=false, append=false, right? Why to change them to ascii=false, append=true

[pmartorell]

No, the default options of vtk_grid are ascii=false, append=true.

Check the following, be aware that the example do not show the defaults. The defaults are written in bullet points.

https://jipolanco.github.io/WriteVTK.jl/v1.16/grids/syntax/#Supported-options

vtk_grid creates DatesetFile with the stated defaults, see:

https://github.com/jipolanco/WriteVTK.jl/blob/55dd5d97644c2fee761a04ea20f95e815b05ad9c/src/WriteVTK.jl#L63

In summary the behaviour (of the proposed implementation) is the following:

• (;) -> ascii=false,append=true : vtk_grid default, writes appended binary
• (;append=false) -> ascii=false,append=false : writes not appended binary
• (;ascii=true) -> ascii=true,append=false : writes in ASCII
• (;ascii=true,append=true) -> ascii=true,append=true : ascii is ignored, writes appended binary