Support changing playback rate (#275)

* initial idea for playback rate

* Add transparency to dropdown

* Move playback speed component to right controls

* Set mpv speed on startup

---------

Co-authored-by: jeffvli <jeffvictorli@gmail.com>

src/renderer/app.tsx

@@ -100,7 +100,8 @@ export const App = () => {
 
             if (!isRunning) {
                 const extraParameters = useSettingsStore.getState().playback.mpvExtraParameters;
-                const properties = {
+                const properties: Record<string, any> = {
+                    speed: usePlayerStore.getState().current.speed,
                     ...getMpvProperties(useSettingsStore.getState().playback.mpvProperties),
                 };