Adds feature flags, and the ability to do browser playback

frontend/src/api/player.tsx

@@ -7,6 +7,12 @@ export interface NowPlayingResponse {
   currentFile: string;
 }
 
+export interface Features {
+  video: boolean;
+  screenshare: boolean;
+  browserPlayback: boolean;
+}
+
 export interface Metadata {
   title?: string;
   description?: string;
@@ -57,6 +63,11 @@ export enum ServerEvent {
 }
 
 export const API = {
+  async getFeatures(): Promise<Features> {
+    const response = await fetch('/api/features');
+    return response.json();
+  },
+
   async getPlaylist(): Promise<PlaylistItem[]> {
     const response = await fetch('/api/playlist');
     return response.json();