Added a contrast effect and the connection needed to apply the video effects to ExoPlayer.
The effect can be applied to the video by checking the "Contrast" card, and use the slider to change the contrast value. The effects are applied when `Apply effects` button is clicked.
PiperOrigin-RevId: 707092041
Added functionality to `Choose preset input` button. The picker allows the user to select a preset input from a list of loaded preset playlists. The selected preset input is then used to populate the ExoPlayer with the corresponding media items.
PiperOrigin-RevId: 704626144
The JSON file contains a list of playlists, each with a name and a list of media items. The EffectActivity loads the JSON file and creates a list of PlaylistHolder objects, which contain the playlist name and the list of media items.
PiperOrigin-RevId: 703069411
Added the functionality for `Choose local file` button to be able to go and select a local file from the device. The file was then displayed by using ExoPlayer inside PlayerView.
PiperOrigin-RevId: 693756565
Added a basic UI to the effect demo app, including a PlayerView, buttons to choose preset input and choose local file, and a button to apply effects. The buttons are currently not implemented, and the app will show a snackbar message when they are clicked.
PiperOrigin-RevId: 693751272
