Add slice syntax to sections permalinks config

Fixes #8363

content/en/content-management/urls.md

@@ -83,7 +83,7 @@ The following is a list of values that can be used in a `permalink` definition i
 : the content's section
 
 `:sections`
-: the content's sections hierarchy
+: the content's sections hierarchy. {{< new-in "0.83.0" >}} Since Hugo 0.83 you can use a selection of the sections using _slice syntax_: `:sections[1:]` includes all but the first, `:sections[:last]` includes all but the last, `:sections[last]` includes only the last, `:sections[1:2]` includes section 2 and 3. Note that this slice access will not throw any out-of-bounds errors, so you don't have to be exact.
 
 `:title`
 : the content's title