Reorganize code in src/markdown.jl

src/markdown.jl

@@ -43,17 +43,34 @@ Supertype of all Markdown AST inline types.
 """
 abstract type AbstractInline <: AbstractElement end
 
+"""
+    isblock(element::AbstractElement) -> Bool
+
+Determines if `element` is a block element (a subtype of [`AbstractBlock`](@ref)).
+"""
+function isblock end
+isblock(::AbstractBlock) = true
+isblock(::AbstractInline) = false
+
+"""
+    isinline(element::AbstractElement) -> Bool
+
+Determines if `element` is an inline element (a subtype of [`AbstractInline`](@ref)).
+"""
+function isinline end
+isinline(::AbstractBlock) = false
+isinline(::AbstractInline) = true
+
 """
     iscontainer(::T) where {T <: AbstractElement} -> Bool
 
 Determines if the particular Markdown element is a container, meaning that is can contain
 child nodes. Adding child nodes to non-container (leaf) nodes is prohibited.
 
-By default, each user-defined element is assumed to be a leaf node by default, and each
-container node should override this method.
+By default, each user-defined element is assumed to be a leaf node, and each container node
+should override this method.
 """
 function iscontainer end
-
 iscontainer(::AbstractElement) = false
 
 """
@@ -68,7 +85,6 @@ elements that are only allowed to have inline child elements or to make sure tha
 If the `parent` element is a leaf node (`iscontainer(parent) === false`)
 """
 function can_contain end
-
 # These methods ensure that, by default, container blocks/inlines are allowed to contain
 # any blocks/inlines (respectively):
 can_contain(parent::AbstractBlock, child::AbstractBlock) = iscontainer(parent)
@@ -77,24 +93,6 @@ can_contain(parent::AbstractInline, child::AbstractInline) = iscontainer(parent)
 # overridden):
 can_contain(parent::AbstractElement, child::AbstractElement) = false
 
-"""
-    isblock(element::AbstractElement) -> Bool
-
-Determines if `element` is a block element (a subtype of [`AbstractBlock`](@ref)).
-"""
-function isblock end
-isblock(::AbstractBlock) = true
-isblock(::AbstractInline) = false
-
-"""
-    isinline(element::AbstractElement) -> Bool
-
-Determines if `element` is an inline element (a subtype of [`AbstractInline`](@ref)).
-"""
-function isinline end
-isinline(::AbstractBlock) = false
-isinline(::AbstractInline) = true
-
 """
     struct Document <: AbstractBlock