Compensate for loss of margin when opening modals
Compensate for loss of margin when opening modals

TODO: Detect system-level RTL setting for left scrollbars.
This fix will still prevent the body from changing width in
all cases.

Bug: T89612
Change-Id: I5052f2572184f43e75ed55ae85eccc8536cbbbd4

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui