Update vignettes to latest recommended API.

[olivroy]

Remove use of cols, and rows to use dims instead. Add examples of wb_dims() usage.
Address #681

I went through the vignettes to see if I could catch some more things.

[JanMarvin]

Just minor nitpicking. You can change it, but I leave this up to you. In all honesty I have to get used to the wb_dims() part, but you are the audience the vignettes are written for. Therefore, who am I to judge 😄

[olivroy]

Thanks ! I addressed the comments, but realized I forgot to review most of conditional-formatting, (done now, mainly rows, cols to dims.

Edit: if it's too soon to advertise wb_dims(), let me know, I will just mention it once in the intro vignette.

[JanMarvin]

Thank you, merged!