terminal-notifier: add shebang line to wrapper

Add shebang line to terminal-notifier to wrapper script. Without this line, the
script fails with "Exec format error" when called outside a shell (e.g. from
the Emacs alert package).

pkgs/applications/misc/terminal-notifier/default.nix

···
     mkdir -p $out/bin
     cp -r terminal-notifier.app $out/Applications
     cat >$out/bin/terminal-notifier <<EOF
+    #!${stdenv.shell}
     cd $out/Applications/terminal-notifier.app
     exec ./Contents/MacOS/terminal-notifier "\$@"
     EOF