Respect GNOME's "Do not disturb" mode

[ekasprzak]

Is your feature request related to a problem? Please describe.
I use GNOME's "Do not disturb" mode when I want to fully focus on something - don't want any notifications, sounds, messages etc.
I generally like SafeEyes' "audible alert" before a break so I know it's coming and I can attempt to finish some part of the task I'm doing before the break hits.
However, it's really not welcomed when I'm in "focus zone" - this sound makes me "jump" sometimes cause of how it sounds.

Describe the solution you'd like
SafeEyes has a "Do not disturb" mode of it's own so it would be perfect if just enabling GNOME's DnD would automatically enable SafeEyes' DnD mode.

Describe alternatives you've considered
I just try to remember to disable SafeEyes everytime I want to enter "focus mode" (but then I almost always forget to enable it back until my eyes start to hurt).

Additional context
I hope the above is clear - if not, let me know, please.

[deltragon]

Can you test if this is fixed now that #571 is merged?