Add script for generating monochrome texture pack for testing.

docs/ncmono.pl

@@ -0,0 +1,26 @@
+#!/usr/bin/perl -w
+# ----------------------------------------------------------------------
+# Create/update a (nearly) monochrome texture pack for NodeCore, for
+# testing the game's accessibility for colorblind users.  All things
+# should be visually distinguishable using luma hints alone, without
+# relying on chroma channels.
+# ----------------------------------------------------------------------
+use strict;
+use warnings;
+use File::Find qw(find);
+use File::Path qw(mkpath);
+
+my $outd = "$ENV{HOME}/.minetest/textures/ncmono";
+
+-d $outd or mkpath($outd);
+-d $outd or die("failed to mkpath $outd");
+
+find(
+	{       wanted => sub {
+			-f $_ and -s $_ and $_ =~ m#\.png$# or return;
+			my $r = system("convert", $_, qw(-colorspace gray), "$outd/$_");
+			$r and die("convert $_ returned $r");
+			print "$_\n";
+		}
+	},
+	"..");