Add announcements (#12662)

* Add announcements

Fix #11006

* Add reactions to announcements

* Add admin UI for announcements

* Add unit tests

* Fix issues

- Add `with_dismissed` param to announcements API
- Fix end date not being formatted when time range is given
- Fix announcement delete causing reactions to send streaming updates
- Fix announcements container growing too wide and mascot too small
- Fix `all_day` being settable when no time range is given
- Change text "Update" to "Announcement"

* Fix scheduler unpublishing announcements before they are due

* Fix filter params not being passed to announcements filter

app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js

@@ -290,6 +290,7 @@ class EmojiPickerDropdown extends React.PureComponent {
     onPickEmoji: PropTypes.func.isRequired,
     onSkinTone: PropTypes.func.isRequired,
     skinTone: PropTypes.number.isRequired,
+    button: PropTypes.node,
   };
 
   state = {
@@ -350,18 +351,18 @@ class EmojiPickerDropdown extends React.PureComponent {
   }
 
   render () {
-    const { intl, onPickEmoji, onSkinTone, skinTone, frequentlyUsedEmojis } = this.props;
+    const { intl, onPickEmoji, onSkinTone, skinTone, frequentlyUsedEmojis, button } = this.props;
     const title = intl.formatMessage(messages.emoji);
     const { active, loading, placement } = this.state;
 
     return (
       <div className='emoji-picker-dropdown' onKeyDown={this.handleKeyDown}>
         <div ref={this.setTargetRef} className='emoji-button' title={title} aria-label={title} aria-expanded={active} role='button' onClick={this.onToggle} onKeyDown={this.onToggle} tabIndex={0}>
-          <img
+          {button || <img
             className={classNames('emojione', { 'pulse-loading': active && loading })}
             alt='🙂'
             src={`${assetHost}/emoji/1f602.svg`}
-          />
+          />}
         </div>
 
         <Overlay show={active} placement={placement} target={this.findTarget}>