Support for multi-row table cells in AsciiDoc output

[manuelfuenmayor]

From https://github.com/metanorma/mn-samples-tex-iso/issues/5

The LaTeX command: \multirow{num_rows}{width}{contents} for multi-row cells, generates a wrong AsciiDoc markup. For example,

This LaTeX code:

...
\usepackage{multirow}
...

\begin{tabular}{ |l|l|l| }
    \hline
    \multirow{4}{*}{Defenders} & LB & Lucas Radebe \\
     & DC & Michael Duburry \\
     & DC & Dominic Matteo \\
     & RB & Didier Domi \\ \hline
    \multirow{3}{*}{Midfielders} & MC & David Batty \\
     & MC & Eirik Bakke \\
     & MC & Jody Morris \\ \hline
\end{tabular}

Results in:

[cols=3*]
|===
| Defenders
| LB
| Lucas Radebe

| DC
| Michael Duburry

| DC
| Dominic Matteo

| RB
| Didier Domi

| Midfielders
| MC
| David Batty

| MC
| Eirik Bakke

| MC
| Jody Morris
|===

However, it should be something like:

[cols=3*]
|===
.4+| Defenders
| LB
| Lucas Radebe

| DC
| Michael Duburry

| DC
| Dominic Matteo

| RB
| Didier Domi

.3+| Midfielders
| MC
| David Batty

| MC
| Eirik Bakke

| MC
| Jody Morris
|===