Modify: add new param_method "copy", "rev", and "REV"

This commit adds new param_method "copy", "rev", and "REV".

It may be possible to express Bitcoin double-hash using the
"REV" introduced this time and the "R" introduced in commit
057fa359.

:KRGS0.1:(s256,s,1)(s256,R,1)(REV,r,1)

The new three param_method "copy", "rev", and "REV" require
caution as they destroy the structure of the KRGS code.
For example, the following will not only cause an infinite
loop, but will also cause the KRGS code to grow larger and
larger.

$ ./koregusu.rb -e ':KRGS0.1:(copy,s,1)' --source="(copy,s,2)"

This commit is related to 057fa359.

koregusu.rb

 #!/usr/bin/env ruby
 #
 # ==========================================================================
-# koregusu0.1 -- version 0.0.99.20250906.3
+# koregusu0.1 -- version 0.0.99.20250906.4
 #
 # written by cleemy desu wayo / Licensed under CC0 1.0
 #
@@ -90,6 +90,12 @@ class KRGS
         new_checksum = Digest::SHA256.hexdigest(key_str)
       when "s512"
         new_checksum = Digest::SHA512.hexdigest(key_str)
+      when "copy"
+        new_checksum = key_str
+      when "rev"
+        new_checksum = key_str.reverse
+      when "REV"
+        new_checksum = key_str.scan(/.{1,2}/).reverse.join
       end
 
       new_param = ""