Replace "suspend mode" by "do not disturb" mode

[bNobo]

The purpose of "suspend mode" is not really clear and can encourage the user to stay in front of their screen for too long (because the countdown is also suspended).

A contrario, the objective of NEEDABREAK! is clear: encourage the user not sit for too long in front of their screen in order to avoid health issues like musculoskeletal disorders, headaches, eye strain.

So "suspend mode" should be remove and replaced by a "do not disturb" mode that would be useful in case of watching a movie or participating to a remote meeting but would not stop the timer. So the user would be invited to make a break as soon as the "do not disturb" mode would be stopped.