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/encode0.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ns1:V2G_Message xmlns:ns1="urn:iso:15118:2:2013:MsgDef" xmlns:ns2="urn:iso:15118:2:2013:MsgHeader" xmlns:ns3="urn:iso:15118:2:2013:MsgBody" xmlns:ns4="urn:iso:15118:2:2013:MsgDataTypes">
+	<ns1:Header>
+		<ns2:SessionID>4142423030303831</ns2:SessionID>
+	</ns1:Header>
+	<ns1:Body>
+		<ns3:WeldingDetectionReq>
+			<ns3:DC_EVStatus>
+				<ns4:EVReady>true</ns4:EVReady>
+				<ns4:EVErrorCode>NO_ERROR</ns4:EVErrorCode>
+				<ns4:EVRESSSOC>100</ns4:EVRESSSOC>
+			</ns3:DC_EVStatus>
+		</ns3:WeldingDetectionReq>
+	</ns1:Body>
+</ns1:V2G_Message>