Add general notifications using rules

[D0miH]

Is your feature request related to a problem? Please describe. In some cases it is useful to get notified if iGlance detects certain behaviour of the machine for several seconds. For example if the cpu utilisation is at 100% for 10 seconds or the memory utilisation is above 80% for 10 seconds.

Describe the solution you'd like The solution would be to add a new item to the sidebar called "Notifications". Here the user can add rules to get notified when the rule is evaluated to true. One example rule would be

Send notification if <selectable_value> is above/below <selectable_value> for <selectable_value> seconds

Describe alternatives you've considered We could include the notification feature into each part of the app (once for memory, once for cpu and once for battery) but this would result in a lot more redundant code.