docs: clarify how to use top-level notes

Update new_fragment.md.j2

Update new_fragment.rst.j2

Update concepts.rst

Update new_fragment.rst.j2

docs/concepts.rst

@@ -29,8 +29,11 @@ fragment, you provide your change information in the appropriate category.
 When the fragments are collected, they are grouped by category into a single
 changelog entry.
 
+Any fragments that do not specify a category are included as top-level
+release notes directly under the release heading.
+
 You can choose not to use categories by setting the :ref:`config_categories`
-setting to empty.
+setting to empty (all notes will appear as top-level release notes).
 
 
 .. _entries:

src/scriv/templates/new_fragment.md.j2

@@ -2,6 +2,7 @@
 A new scriv changelog fragment.
 
 Uncomment the section that is right (remove the HTML comment wrapper).
+For top level release notes, leave all the headers commented out.
 -->
 
 {% for cat in config.categories -%}

src/scriv/templates/new_fragment.rst.j2

@@ -1,7 +1,8 @@
 .. A new scriv changelog fragment.
 {% if config.categories -%}
 ..
-.. Uncomment the header that is right (remove the leading dots).
+.. Uncomment the section that is right (remove the leading dots).
+.. For top level release notes, leave all the headers commented out.
 ..
 {% for cat in config.categories -%}
 .. {{ cat }}