Add support for pipe input and file extension handling

- Added stdin pipe support for both encode and decode operations
- Implemented file extension-based processing:
  * .dump files: hex dump format with arrow separators
  * .hex files: pure hex string data
  * .xml files: XML content for encoding
- Added 'filename --encode' and 'filename --decode' syntax support
- Enhanced command line parsing for flexible usage
- Updated help text with pipe usage examples

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Data/dump1.dump

@@ -0,0 +1,7 @@
+0000   10 22 33 44 55 66 80 34 28 2e 23 dd 86 dd 60 00   ."3DUf.4(.#...`.
+0010   00 00 00 33 06 ff fe 80 00 00 00 00 00 00 82 34   ...3...........4
+0020   28 ff fe 2e 23 dd fe 80 00 00 00 00 00 00 12 22   (...#.........."
+0030   33 ff fe 44 55 66 d1 21 c3 65 2c c5 4a 3c 00 63   3..DUf.!.e,.J<.c
+0040   9b 49 50 18 0b 26 2f bd 00 00 01 fe 80 01 00 00   .IP..&/.........
+0050   00 17 80 98 02 10 50 90 8c 0c 0c 0e 0c 51 e0 20   ......P......Q. 
+0060   25 69 68 c0 c0 c0 c0 c0 80                        %ih......