Added multicite-versions of biblatex-commands

[frankbits]

Fix #3524

Summary of additions and changes

• added multicite-versions of biblatex-commands (based on biblatex documentation

NOTE: (see Inconistency in biblatex documentation)

• \Fvolcite defined in LatexBiblatexCommand.kt and CommandMagic.kt but not explicitely in biblatex documentation.
• maybe missing a multicite-command or/and added a non-existent one

Inconistency in biblatex documentation

The biblatex documentation defines \fvolcite and \ftvolcite, but defines multicite-versions of \fvolcite and \Fvolcite.
So for some reason the documentation of biblatex defines a multicite-version of a non-existent command (\Fvolcite), while not defining one for an existing one (\ftvolcite).
As \fvolcite and \ftvolcite are based on \footcite and \footcitetext I think a captalized version of either does not exist.
On the other hand I don't know if \Fvolcites actually exists, and if it does, if it's a multicite-version for \ftvolcite or if there maybe is another undocumented one for that.

biblatex documentation (page 115)

\fvolcite[hprenotei]{hvolumei}[hpagesi]{hkeyi}
\ftvolcite[hprenotei]{hvolumei}[hpagesi]{hkeyi}
Similar to \volcite but based on \footcite and \footcitetext, respectively.

\fvolcites(hmultiprenotei)(hmultipostnotei)[hprenotei]{hvolumei}[hpagesi]{hkeyi}...[hprenotei]{hvolumei}[hpagesi]{hkeyi}
\Fvolcites(hmultiprenotei)(hmultipostnotei)[hprenotei]{hvolumei}[hpagesi]{hkeyi}...[hprenotei]{hvolumei}[hpagesi]{hkeyi}
The multicite version of \fvolcite and \Fvolcite, respectively

Didn't have the time to really analyse/test this yet. Maybe someone else knows more about this or can find out more.

How to test this pull request

\cites{cite1}[pre][post]{cite2}[post]{cite3}[pre][]{cite4}
\cites{cite5, cite6}[pre][post]{cite7, cite8}[post]{cite9, cite10}[pre][]{cite11, cite12}
\cites(listpre)(listpost)[post]{cite1}{cite2,cite3}
\ldots % other combinations, other multicite-commands

• Updated the documentation, or no update necessary
• Added tests, or no tests necessary

[PHPirates]

Thanks a lot! I will double check what is going on with \Fvolcite and \ftvolcites, it appears that they both do exist