message: add comment blip to feed controls
diff: <!--
  If we require tabs, then there is no reason to show the reply button.
  -->
  - <button class="btn btn-outline btn-sparse btn-circle"
  + <button
  + class="btn btn-outline btn-sparse btn-circle"
  v-if="!requireTabs"
  @click="toggleComments"
  v-app-tooltip="$gettext( 'Comment on This Post' )"
  >
  <app-jolticon icon="comment" />
  </button>
  + <span
  + class="blip light filled"
  + v-if="!requireTabs && post.comment_count > 0"
  + >
  + <span class="blip-caret"></span>
  + <span class="blip-count">
  + {{ post.comment_count | number }}
  + </span>
  + </span>
  <app-fireside-post-like-widget
  :post="post"
  :circle="true"
  />
  - <button class="btn btn-outline btn-sparse btn-circle"
  + <button
  + class="btn btn-outline btn-sparse btn-circle"
  v-app-popover-trigger="sharePopoverId"
  v-app-tooltip="$gettext( 'Share' )"
  >
  