[FEATURE] Add notification when a task completed

[Kiawaik]

Currently, there is no notification to alert the player when a task is complete. Players need to monitor themselves by looking at the memo to determine which was just completed. They may also be looking for available staff for another task. A notification can let the player know better which task is going to the new stage and which staff is free now.

1. We can add a notification bar in the bottom left corner to alert the player of what tasks have been done and which staff has done it. (Shows "Map Lv1 Database Development Finished By William")

2. Add a small icon to a task where it is newly available. more intuitive let the player know which task is new.

3. There can be a sound alert to alert the player that the task is finished. It is an additional way to alert players some task was finished and there are free staff can assign.

These above actions can help players easily know when a task is going to a new stage, then assign new tasks to staff after they know a task is completed and some staff is available.

[Alexachenggg]

Agree that it would be more convenient for users if the game provided task notifications. And I think a lot of users forget to check the memo, because first they have to go back to home. For the sake of the game's progress, most of them (including me) would not look for two pages.