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

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

packages/camera/pubspec.yaml

@@ -0,0 +1,21 @@
+name: camera_elinux
+description: A Flutter plugin for getting information about and controlling the
+  camera on eLinux. Supports previewing the camera feed, capturing images, capturing video,
+  and streaming image buffers to dart.
+version: 0.1.0
+homepage: https://github.com/sony/flutter-elinux-plugins
+repository: https://github.com/sony/flutter-elinux-plugins/tree/main/packages/camera
+
+environment:
+  sdk: ">=2.12.0 <3.0.0"
+  flutter: ">=1.20.0"
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+flutter:
+  plugin:
+    platforms:
+      elinux:
+        pluginClass: CameraElinuxPlugin