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/encode2.xml

@@ -0,0 +1,22 @@
+<?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>41424230303038313</ns2:SessionID>
+	</ns1:Header>
+	<ns1:Body>
+		<ns3:PreChargeRes>
+			<ns3:ResponseCode>OK</ns3:ResponseCode>
+			<ns3:DC_EVSEStatus>
+				<ns4:NotificationMaxDelay>0</ns4:NotificationMaxDelay>
+				<ns4:EVSENotification>None</ns4:EVSENotification>
+				<ns4:EVSEIsolationStatus>Valid</ns4:EVSEIsolationStatus>
+				<ns4:EVSEStatusCode>EVSE_Ready</ns4:EVSEStatusCode>
+			</ns3:DC_EVSEStatus>
+			<ns3:EVSEPresentVoltage>
+				<ns4:Multiplier>0</ns4:Multiplier>
+				<ns4:Unit>V</ns4:Unit>
+				<ns4:Value>394</ns4:Value>
+			</ns3:EVSEPresentVoltage>
+		</ns3:PreChargeRes>
+	</ns1:Body>
+</ns1:V2G_Message>