Added TimelineQueueButtonHeader component, styles

button at top of feeds to show "click to load more"

app/javascript/gabsocial/components/timeline_queue_button_header.js

@@ -0,0 +1,38 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { FormattedMessage } from 'react-intl';
+import { shortNumberFormat } from '../utils/numbers';
+
+export default class TimelineQueueButtonHeader extends React.PureComponent {
+  static propTypes = {
+    onClick: PropTypes.func.isRequired,
+    count: PropTypes.number,
+    itemType: PropTypes.string,
+  };
+
+  static defaultProps = {
+    count: 0,
+    itemType: 'item',
+  };
+
+  render () {
+    const { count, itemType, onClick } = this.props;
+
+    if (count <= 0) return null;
+
+    return (
+      <div className='timeline-queue-header'>
+        <a className='timeline-queue-header__btn' onClick={onClick}>
+          <FormattedMessage
+            id='timeline_queue.label'
+            defaultMessage='Click to see {count} new {type}'
+            values={{
+              count: shortNumberFormat(count),
+              type: count == 1 ? itemType : `${itemType}s`,
+            }}
+          />
+        </a>
+      </div>
+    );
+  }
+}