Add table ID to LaTeX output

[tarleb]

The identifier of a table is lost when converting to LaTeX, making it impossible to reference and crosslink to the table from within the document.

pandoc -f html -t latex
<table id="test">
  <tr><td>one</td><td>two</td></tr>
</table>
^D
\begin{longtable}[]{@{}ll@{}}
\toprule()
\endhead
one & two \\
\bottomrule()
\end{longtable}

The hypertarget should probably be added to the caption if one exists, or elsewhere in the table if the caption is empty.