Adds X::Comp to neato-ized files

Check [IRC
log](discussion](https://irclog.perlgeek.de/perl6/2018-03-23#i_15958129))
for discussion. Also related to #246 (although it's closed).

Kudos and 👍 to @AlexDaniel for help.

Author: JJ

lib/Perl6/TypeGraph/Viz.pm6

@@ -101,7 +101,7 @@ class Perl6::TypeGraph::Viz {
             run 'dot', '-V', :!err or die 'dot command failed! (did you install Graphviz?)';
         }
         die "bad filename '$file'" unless $file;
-        my $graphvizzer = ( $file ~~ /Metamodel\:\:/ )??'neato'!!'dot';
+        my $graphvizzer = ( $file ~~ /Metamodel\:\: || X\:\:Comp/ )??'neato'!!'dot';
         spurt $file ~ ‘.dot’, self.as-dot(:$size).encode; # raw .dot file for debugging
         my $dot = Proc::Async.new(:w, $graphvizzer, '-T', $format, '-o', $file);
         my $promise = $dot.start;