docs(OverflowMenu): expose OverflowMenuContext in docs (#12587)

* docs(OverflowMenu): expose OverflowMenuContext in docs

* update wording

Author: kmcfaul

packages/react-core/src/components/OverflowMenu/examples/OverflowMenu.md

@@ -19,6 +19,8 @@ import AlignCenterIcon from '@patternfly/react-icons/dist/esm/icons/align-center
 import AlignRightIcon from '@patternfly/react-icons/dist/esm/icons/align-right-icon';
 import RhUiEllipsisVerticalFillIcon from '@patternfly/react-icons/dist/esm/icons/rh-ui-ellipsis-vertical-fill-icon';
 
+`OverflowMenuContext` is also available to import and use to further customize and refine behaviors that should respect responsive breakpoints. This context provides the `isBelowBreakpoint` boolean that will update when the specified breakpoint is reached.
+
 ## Examples
 
 ### Simple (responsive)