Add script to simulate Hush supply

contrib/hush_supply

@@ -0,0 +1,26 @@
+#!/usr/bin/env perl
+use warnings;
+use strict;
+
+my $supply = 0.0;
+my $block  = 0;
+my $amount = 12.5;
+my $halvings = 0;
+
+while ($supply <= 21_000_000) {
+#while ($halvings <= 64 && $amount >= 1e-8) {
+    $block++;
+    if ($block < 5) {
+        $amount = 40_000;
+    } else {
+        # Halving every 840000 blocks
+        if ($block % 840_000 == 0) {
+            $amount /= 2;
+            $halvings++;
+        }
+        $amount = 12.5 / (2**$halvings);
+    }
+    $supply += $amount;
+    # block, current supply, block reward amount, number of halvings
+    print "$block,$supply,$amount,$halvings\n";
+}