Added docstrings and AbstractArrayPartition type

After @ChrisRackauckas comments I have documented how to subtype from AbstractNamedArrayPartition as well as added an AbstractArrayPartition type which both AbstractNamedArrayPartition and ArrayPartition subtype from

Author: htsnowden

src/array_partition.jl

@@ -1,3 +1,5 @@
+abstract type AbstractArrayPartition{T} <: AbstractVector{T} end
+
 """
 ```julia
 ArrayPartition(x::AbstractArray...)
@@ -23,7 +25,7 @@ A = ArrayPartition(y, z)
 
 we would have `A.x[1]==y` and `A.x[2]==z`. Broadcasting like `f.(A)` is efficient.
 """
-struct ArrayPartition{T, S <: Tuple} <: AbstractVector{T}
+struct ArrayPartition{T, S <: Tuple} <: AbstractArrayPartition{T}
     x::S
 end
 

src/named_array_partition.jl

@@ -1,4 +1,20 @@
-abstract type AbstractNamedArrayPartition{T, A, NT} <: AbstractVector{T} end
+"""
+    AbstractNamedArrayPartition{T, A, NT}
+
+An abstract type above that of `NamedArrayPartition` that can be used to subtype a
+new and seperately named 'NamedArrayPartition'-like structure. This can be done
+by defining your new type as:
+
+```julia
+struct foo{T, A <: ArrayPartition{T}, NT <: NamedTuple} <: AbstractNamedArrayPartition{T, A, NT}
+    array_partition::A
+    names_to_indices::NT
+end
+```
+
+where `foo` is your custom name and then all funcitonalities of NamedArrayPartitions will be inherited.
+"""
+abstract type AbstractNamedArrayPartition{T, A, NT} <: AbstractArrayPartition{T} end
 
 """
     NamedArrayPartition(; kwargs...)