Compat annotation for #29890 (broadcasting CartesianIndices).

Author: fredrikekre

base/multidimensional.jl

@@ -211,6 +211,28 @@ module IteratorsMD
     CartesianIndex(1, 2)
     ```
 
+    ## Broadcasting
+
+    `CartesianIndices` support broadcasting arithmetic (+ and -) with a `CartesianIndex`.
+
+    !!! compat "Julia 1.1"
+    Broadcasting of CartesianIndices requires at least Julia 1.1.
+
+    ```jldoctest
+    julia> CIs = CartesianIndices((2:3, 5:6))
+    2×2 CartesianIndices{2,Tuple{UnitRange{Int64},UnitRange{Int64}}}:
+     CartesianIndex(2, 5)  CartesianIndex(2, 6)
+     CartesianIndex(3, 5)  CartesianIndex(3, 6)
+
+    julia> CI = CartesianIndex(3, 4)
+    CartesianIndex(3, 4)
+
+    julia> CIs .+ CI
+    2×2 CartesianIndices{2,Tuple{UnitRange{Int64},UnitRange{Int64}}}:
+     CartesianIndex(5, 9)  CartesianIndex(5, 10)
+     CartesianIndex(6, 9)  CartesianIndex(6, 10)
+    ```
+
     For cartesian to linear index conversion, see [`LinearIndices`](@ref).
     """
     struct CartesianIndices{N,R<:NTuple{N,AbstractUnitRange{Int}}} <: AbstractArray{CartesianIndex{N},N}