Add 'doc' target accidentally removed during migration

mkit.ini

     PREFIX = /usr/local
 
 [roots]
+    doc     = [ENV:PREFIX]/share/shellfu-bash-saturnin
     sfmod   = [ENV:PREFIX]/share/shellfu/include-bash
 
 [files]

packaging/template.spec

 %make_install
 
 %files
+%doc /usr/local/share/shellfu-bash-saturnin/README.md
 /usr/local/share/shellfu/include-bash/saturnin.sh