Add vignette for 'visualising-xmaps'

[cynthiahqy]

Eventually will showcase visualisation designs and helpers in #56

For now just illustrate possible vis types using anzsco22 to isco8:

• [x] bigraph
• [x] matrix
• [ ] fancy print (with arrows between)

Example crosswalks:

• [x] ANZSCO22 to ISCO8: excel download

Include any useful functions/abstractions from viz-panel-maps and the create-conformr docs; and sample code in #56.

Does it make sense to include this vignette in the package? Or maybe just as an article on the pkgdown?

[cynthiahqy]

Why is the vignette build not using xmap::print.xmap_df()???

Do I need to do #96

[cynthiahqy]

closed with 78403c3f3e60e5d44e7aaf192438207c64ef2158