Add ability to update thumbnail and preview on client

shared/models/config/server-config.model.ts

@@ -23,6 +23,12 @@ export interface ServerConfig {
   }
 
   video: {
+    image: {
+      size: {
+        max: number
+      }
+      extensions: string[]
+    },
     file: {
       extensions: string[]
     }

shared/models/videos/video-update.model.ts

@@ -11,4 +11,6 @@ export interface VideoUpdate {
   tags?: string[]
   commentsEnabled?: boolean
   nsfw?: boolean
+  thumbnailfile?: Blob
+  previewfile?: Blob
 }