build/pkgs: Mark some more packages with tag 'front-end'

Author: Matthias Koeppe

build/pkgs/pandoc/front-end

@@ -106,8 +106,8 @@ for PKG_BASE in $(sage-package list --has-file SPKG.rst --has-file math :standar
 done >> "$OUTPUT_INDEX"
 cat >> "$OUTPUT_INDEX" <<EOF
 
-Front-end and graphics
-~~~~~~~~~~~~~~~~~~~~~~
+Front-end, graphics, document preparation
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 EOF
 for PKG_BASE in $(sage-package list --has-file SPKG.rst --no-file math --has-file front-end :standard: | grep -v '^sagemath_'); do