docs: update documentation

Author: mrholek

docs/4.0/components/CHeader.mdx

@@ -40,7 +40,7 @@ Here's what you need to know before getting started with the header:
 
 - Headers require a wrapping `.header` with `.header-expand{-sm|-md|-lg|-xl|-xxl}` for responsive collapsing and [color scheme](#color-schemes) classes.
 - Headers and their contents are fluid by default. Change the [container](#containers) to limit their horizontal width in different ways.
-- Use our [spacing](https://coreui.io/docs/utilities/spacing" >}}) and [flex](https://coreui.io/docs/4.0/utilities/flex) utility classes for controlling spacing and alignment within headers.
+- Use our [spacing](https://coreui.io/docs/utilities/spacing") and [flex](https://coreui.io/docs/4.0/utilities/flex) utility classes for controlling spacing and alignment within headers.
 - Headers are responsive by default, but you can easily modify them to change that. Responsive behavior depends on our Collapse JavaScript plugin.
 - Ensure accessibility by using a `<nav>` element or, if using a more generic element such as a `<div>`, add a `role="navigation"` to every header to explicitly identify it as a landmark region for users of assistive technologies.
 - Indicate the current item by using `aria-current="page"` for the current page or `aria-current="true"` for the current item in a set.

docs/4.0/components/CListGroup.mdx

@@ -203,6 +203,8 @@ Place CoreUI's checkboxes and radios within list group items and customize as ne
   </CListGroup>
 </Playground>
 
+TODO: add missing examples from base docs
+
 
 ## API