feat(cw-button): Add aria controls to CW trigger (#2303)

Add an ID to the CW spoiler input field to give aria-controls a handle on it. Pass that id to the CW trigger button. Modify text icon button component to accept aria controls id value. Add aria-expanded value to text icon button to indicate when it is expanded.

app/assets/javascripts/components/features/compose/containers/spoiler_button_container.jsx

@@ -10,7 +10,8 @@ const messages = defineMessages({
 const mapStateToProps = (state, { intl }) => ({
   label: 'CW',
   title: intl.formatMessage(messages.title),
-  active: state.getIn(['compose', 'spoiler'])
+  active: state.getIn(['compose', 'spoiler']),
+  ariaControls: 'cw-spoiler-input'
 });
 
 const mapDispatchToProps = dispatch => ({