gnu: poppler: Add poppler-data.

In order to make poppler support CJK and Cyrillic scripts, one of the
following has to be done:
1. Build poppler with poppler-data as input.
2. Add poppler-data into poppler's output path.
A simple union-build is not enough, as reported in
<https://issues.guix.gnu.org/53536>.

* gnu/packages/pdf.scm (poppler)[inputs]: Add poppler-data.

Signed-off-by: Liliana Marie Prikler <liliana.prikler@gmail.com>

gnu/packages/pdf.scm

@@ -242,6 +242,7 @@ please install the @code{flyer-composer-gui} package.")))
              ("libtiff" ,libtiff)
              ("lcms" ,lcms)
              ("openjpeg" ,openjpeg)
+             ("poppler-data", poppler-data)
              ("zlib" ,zlib)
 
              ;; To build poppler-glib (as needed by Evince), we need Cairo and