Add linescan plugin for line scan camera simulation

- New plugin extracts single row/column from frames and builds line scan image
- Supports horizontal mode (extract row, stack vertically)
- Supports vertical mode (extract column, stack horizontally)
- Configurable line index and output size
- Proper caps negotiation with fixate_caps implementation
- Updated build system to include linescan plugin
- Added comprehensive README with usage examples

gst/linescan/CMakeLists.txt

@@ -0,0 +1,28 @@
+set (SOURCES
+  gstlinescan.c
+  )
+    
+set (HEADERS
+  gstlinescan.h)
+    
+include_directories (AFTER
+  ${ORC_INCLUDE_DIR})
+
+set (libname gstlinescan)
+
+add_library (${libname} MODULE
+  ${SOURCES}
+  ${HEADERS})
+  
+target_link_libraries (${libname}
+  ${ORC_LIBRARIES}
+  ${GLIB2_LIBRARIES}
+  ${GOBJECT_LIBRARIES}
+  ${GSTREAMER_LIBRARY}
+  ${GSTREAMER_BASE_LIBRARY}
+  ${GSTREAMER_VIDEO_LIBRARY})
+  
+if (WIN32)
+  install (FILES $<TARGET_PDB_FILE:${libname}> DESTINATION ${PDB_INSTALL_DIR} COMPONENT pdb OPTIONAL)
+endif ()
+install(TARGETS ${libname} LIBRARY DESTINATION ${PLUGIN_INSTALL_DIR})