add a docstring for Rect and its aliases

src/primitives/rectangles.jl

@@ -14,6 +14,21 @@ end
 ##
 # Constructors & typealiases
 
+"""
+    const Rect{N,T} = HyperRectangle{N,T}
+
+A rectangle in N dimensions, formally the caartesian product of intervals. See also [`HyperRectangle`](@ref). Its aliases are
+
+|Dimensions|Generic    |Float32   |Int       |
+|----------|-----------|----------|----------|
+|Any       |`Rect{N,T}`|`Rectf{N}`|`Recti{N}`|
+|2         |`Rect2{T}` |`Rect2f`  |`Rect2i`  |
+|3         |`Rect3{T}` |`Rect3f`  |`Rect3i`  |
+
+and `RectT{T} = Rect{N,T} where {N}`.
+"""
+Rect, Rect2, Rect3, RectT, Rectf, Rect2f, Rect3f, Recti, Rect2i, Rect3i
+
 const Rect{N,T} = HyperRectangle{N,T}
 const Rect2{T} = Rect{2,T}
 const Rect3{T} = Rect{3,T}