Re: support figure space (U+2007)

[Masamichi Hosoda]

>> the /a "flag" can also be used to limit the character class to ASCII
>> space characters:
>>  
>> -  $content =~ s/^\s*//;
>> -  $content =~ s/\s*$//;
>> +  $content =~ s/^\s*//a;
>> +  $content =~ s/\s*$//a;
> 
> This looks good, thanks.  However, it is probably necessary to filter
> out the ideographic space (U+3000), too.
> 
> Masamichi-san, what do you think?  Here is a link to the complete
> conversation:
> 
>   https://lists.gnu.org/archive/html/bug-texinfo/2022-01/msg00005.html
> 
> Other CJK users, please also comment!

I think it is not necessary to filter out U+3000.

In the widely used Japanese TeX system (pTeX, upTeX, and LuaTeX-ja),
U+3000 is output as-is and is not filtered out.
Processing the following `.tex` containing U+3000 with lualatex,
you get a PDF that looks right-aligned.

```
\documentclass{ltjsarticle}

\begin{document}

\begin{tabular}{ll}
  ^^^^3000^^^^3000^^^^3042 & ^^^^3000^^^^3000^^^^3042 \\
  ^^^^3000^^^^3042^^^^3042 & ^^^^3000^^^^3042^^^^3042 \\
  ^^^^3042^^^^3042^^^^3042 & ^^^^3042^^^^3042^^^^3042 \\
\end{tabular}

\end{document}
```