Initial video support

example/assets/sample_data.json

@@ -17,6 +17,11 @@
          "style":"display: block; margin: auto;"
       }
    },
+   {
+      "insert": {
+         "video": "https://www.youtube.com/watch?v=V4hgdKhIqtc&list=PLbhaS_83B97s78HsDTtplRTEhcFsqSqIK&index=1"
+      }
+   },
    {
       "insert":"\nRich text editor for Flutter"
    },

lib/src/models/documents/nodes/embed.dart

@@ -39,4 +39,7 @@ class BlockEmbed extends Embeddable {
 
   static const String imageType = 'image';
   static BlockEmbed image(String imageUrl) => BlockEmbed(imageType, imageUrl);
+
+  static const String videoType = 'video';
+  static BlockEmbed video(String videoUrl) => BlockEmbed(videoType, videoUrl);
 }