Play sound effect (bell) before and after break

[AllanChain]

See also #3

This feature can be handy when using a computer at home. During the break, the user may switch to other tasks and leave. A bell informs the user, who might in another room, that the break has ended, and they can go back to use the computer.

This feature requires:

• Creating bells. I choose to use LMMS to avoid copy right issues
• Qt Multimedia lib is required to build, which may increase binary size

[AllanChain]

Play sound before break can also be helpful. For example, the user is using a smartphone or writing on paper and is unaware of breaks.

[wolftune]

ideally, this should be customizable, let user choose their own sounds if they like

[AllanChain]

ideally, this should be customizable, let user choose their own sounds if they like

With the current version (4e9d70c), users can already choose the sound or even use local sound files.