jsonfmt: Add max_size and max_depth options

FU/Util.pod

@@ -45,6 +45,25 @@ be sufficient. The following is probably an improvement:
 
     json_format($data) =~ s{</}{<\\/}rg =~ s/<!--/<\\u0021--/rg;
 
+The following C<%options> are supported:
+
+=over
+
+=item utf8
+
+When set to a true value, returns a UTF-8 encoded byte string instead of a Perl
+Unicode string.
+
+=item max_size
+
+Maximum permitted size, in bytes, of the generated JSON string. Defaults to 1 GiB.
+
+=item max_depth
+
+Maximum permitted nesting depth of Perl values. Defaults to 512.
+
+=back
+
 =back
 
 (Why the hell yet another JSON codec when CPAN is already full of them!? Well,