shutter: add missing dependencies for Screenshot->Export (Ctrl+U) support

However, none of the exporters I tried actually _worked_, but now
shutter at least returns an error to the user (pop-up UI element)
instead of silently hanging and only leaving messages on stdout/stderr
about the missing deps.

AFAICS, this changes the failure of Screenshot->Export functionality
from a packaging bug to an application bug (upstream).

pkgs/applications/graphics/shutter/default.nix

@@ -8,6 +8,7 @@ let
       ProcProcessTable URI ImageExifTool Gtk2AppIndicator LWPUserAgent JSON
       PerlMagick WWWMechanize HTTPDate HTMLForm HTMLParser HTMLTagset JSONXS
       CommonSense HTTPCookies NetOAuth PathClass GooCanvas X11Protocol Cairo
+      EncodeLocale TryTiny TypesSerialiser LWPMediaTypes
     ];
 in
 stdenv.mkDerivation rec {