Ability to disable auto refetch

[swanysimon]

Is your feature request related to a problem? Please describe.
I'm often in between good internet connections, and when gh dash auto refreshes when I'm on a plane or something, the error message obscures part of the screen and I haven't found a way to recover from it without waiting for internet and refreshing

Describe the solution you'd like
With a 0 value to refetchIntervalMinutes, don't ever auto refresh

Describe alternatives you've considered
There are many ways to do this. You could take false, or null, or a negative number, or have a separate configuration key to disable. <= 0 seemed like a reasonable start, as it currently just fires off requests nonstop (maybe should file as a bug? eh)

Additional context
I should have taken a screenshot on my flight yesterday but the dashboard was left completely unusable