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/dump2.dump

@@ -0,0 +1,7 @@
+0000   80 34 28 2e 23 dd 10 22 33 44 55 66 86 dd 60 00   .4(.#.."3DUf..`.
+0010   00 00 00 2c 06 ff fe 80 00 00 00 00 00 00 12 22   ...,..........."
+0020   33 ff fe 44 55 66 fe 80 00 00 00 00 00 00 82 34   3..DUf.........4
+0030   28 ff fe 2e 23 dd c3 65 d1 21 00 7d 20 74 2c e1   (...#..e.!.} t,.
+0040   d2 0a 50 18 11 1c 49 71 00 00 01 fe 80 01 00 00   ..P...Iq........
+0050   00 10 80 98 02 10 50 90 8c 0c 0c 0e 0c 52 11 00   ......P......R..
+0060   32 00                                             2.