message: Add SubNav with search bar documentation.
diff: @@ -23,6 +23,20 @@ This ensures that the NavLink gets `activeClassName='selected'`
  </SubNav>
  ```
  +## SubNav with search example
  +
  +```jsx live
  +<SubNav aria-label="Main">
  + <SubNav.Link href="#home" selected>
  + Home
  + </SubNav.Link>
  + <SubNav.Link href="#documentation">Documentation</SubNav.Link>
  + <SubNav.Link href="#support">Support</SubNav.Link>
  +
  + <SubNav.Search />
  +</SubNav>
  +```
  +
  ## System props
  SubNav and SubNav.Link components get `COMMON` system props. Read our [System Props](/system-props) doc page for a full list of available props.
  