add perl6 code for chapters 1-4 (#49)

03_recursion/perl6/03_factorial.p6

@@ -0,0 +1,7 @@
+#!/usr/bin/env perl6
+use v6.c;
+
+multi fact(1) { 1 }
+multi fact($x where { $x > 1 }) { $x * fact($x-1) }
+
+say fact(5);