docs: add link to Hugo docs to explain page weight (#637)

exampleSite/content/en/usage/configuration.md

@@ -269,7 +269,9 @@ params:
 # Set type to 'posts' if you want to render page as blogpost
 type = "posts"
 
-# Set page weight to re-arrange items in file-tree menu.
+# Hugo predefined front matter variable, to re-arrange items in file-tree menu
+# See weights section of
+# https://gohugo.io/content-management/front-matter/#predefined
 weight = 10
 
 # Set how many table of contents levels to be showed on page.