Add volume numbers in outline (from test)

[berger-n]

Maybe easiest to prepend to the volume title

[berger-n]

done: https://library-dev.bdrc.io/show/bdr:MW22084

in etexts as well: link

@eroux @roopeux feel free to tell me how I should fine tune this / when not to show the index number maybe?

[roopeux]

It looks great @berger-n. To alleviate the slight cosmetic issue with numbered volumes, maybe always add a right bracket: "14) volume 14"

[berger-n]

thanks @roopeux good idea! done: https://library-dev.bdrc.io/show/bdr:MW22084

[eroux]

that's nice but also a bit confusing.. maybe we can keep the volume number for nodes of type volume only? Having the numbers for sections, texts, etc. is a bit puzzling (I actually can't make sense of the screenshot from the previous comment)

[berger-n]

done: https://library-dev.bdrc.io/show/bdr:MW22084