add note to select_with_search on accessibility issues

issues with Voice Over compatibility where flagged
in our accessibility audit [1]

```
After using text search, the organisation list of
options aren’t announced using keyboard arrow
up/down. Tested with Safari + VoiceOver.

Users should be able to access this list using a
keyboard or other input methods, with each item
being announced along with a count of the total
number of options.
```

I don't think there is an easy way for us to fix
these as the component relies on an external
library, Choices. I managed to use the
`autocomplete` component and get the same
functionality and meet accessibility requirements by passing in

```
    autocomplete_configuration_options: {
      showAllValues: true,
    },
```

[1] https://trello.com/c/t8Yu5ImI/793-combobox-lead-organisations-names-should-be-announced-with-a-text-reader-severe

app/views/components/docs/select_with_search.yml

@@ -1,6 +1,10 @@
 name: Select with search
 description: A dropdown select with search
 body: |
+  NOTE: this component currently fails WCAG compliance for keyboard navigation, as the total number of options are not 
+  announced when using Voice Over - the [autocomplete](./autocomplete.yml) component can provide same functionality and 
+  meets the accessibility requirements.
+  
   Use this component to create a JavaScript-enhanced dropdown select.
 
   It's powered by [Choices.js][], which is similar to [Select2][] but without the jQuery dependency.