[camera][draft] Add camera plugin (#29)

Added the first draft version, but there are still a lot of unimplemented features.

packages/camera/example/elinux/flutter/generated_plugins.cmake

@@ -0,0 +1,17 @@
+#
+# Generated file, do not edit.
+#
+
+list(APPEND FLUTTER_PLUGIN_LIST
+  camera_elinux
+  video_player_elinux
+)
+
+set(PLUGIN_BUNDLED_LIBRARIES)
+
+foreach(plugin ${FLUTTER_PLUGIN_LIST})
+  add_subdirectory(flutter/ephemeral/.plugin_symlinks/${plugin}/elinux plugins/${plugin})
+  target_link_libraries(${BINARY_NAME} PRIVATE ${plugin}_plugin)
+  list(APPEND PLUGIN_BUNDLED_LIBRARIES $<TARGET_FILE:${plugin}_plugin>)
+  list(APPEND PLUGIN_BUNDLED_LIBRARIES ${${plugin}_bundled_libraries})
+endforeach(plugin)