Currently waybar _can_ try to start even if there's no graphical session (and
no sway) running. Adding `Requisite=` prevents this. From `systemd.unit(5)`:
Requisite=
Similar to Requires=. However, if the units listed here are not
started already, they will not be started and the starting of
this unit will fail immediately. Requisite= does not imply an
ordering dependency, even if both units are started in the same
transaction. Hence this setting should usually be combined with
After=, to ensure this unit is not started before the other
unit.
When Requisite=b.service is used on a.service, this dependency
will show as RequisiteOf=a.service in property listing of
b.service. RequisiteOf= dependency cannot be specified directly.
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