Set MultiRegionField with Number (#4489)

Author: siddharthabishnu

src/MultiRegion/multi_region_field.jl

@@ -120,6 +120,9 @@ end
 set!(mrf::MultiRegionField, v)  = apply_regionally!(set!,  mrf, v)
 fill!(mrf::MultiRegionField, v) = apply_regionally!(fill!, mrf, v)
 
+set!(mrf::MultiRegionField, a::Number)  = apply_regionally!(set!,  mrf, a)
+fill!(mrf::MultiRegionField, a::Number) = apply_regionally!(fill!, mrf, a)
+
 set!(mrf::MultiRegionField, f::Function) = apply_regionally!(set!, mrf, f)
 set!(u::MultiRegionField, v::MultiRegionField) = apply_regionally!(set!, u, v)
 compute!(mrf::GriddedMultiRegionField, time=nothing) = apply_regionally!(compute!, mrf, time)