This BetterDiscord plugin automatically enables Do Not Disturb (other options available) mode when your activity is set to "Playing a game." It will automatically back to Online when the game activity is no longer displayed. This plugin is useful for those who want to focus on the game and don't want to be disturbed by notifications.
I know plugin's code is kind of messy, but it works. I will try to improve it in the future. If you have any suggestions or improvements, feel free to create a pull request or open an issue.