Add extensibility point for d-editor

app/assets/javascripts/discourse/templates/components/composer-editor.hbs

@@ -1,4 +1,5 @@
-{{d-editor tabindex="4"
+{{d-editor
+  tabindex="4"
   value=composer.reply
   placeholder="composer.reply_placeholder"
   previewUpdated="previewUpdated"
@@ -13,8 +14,9 @@
   composerEvents=true
   onExpandPopupMenuOptions="onExpandPopupMenuOptions"
   onPopupMenuAction=onPopupMenuAction
-           popupMenuOptions=popupMenuOptions}}
+  popupMenuOptions=popupMenuOptions
+  outletArgs=(hash composer=composer editorType="composer")}}
 
 {{#if site.mobileView}}
-    <input type="file" id="mobile-uploader" multiple />
+  <input type="file" id="mobile-uploader" multiple>
 {{/if}}

app/assets/javascripts/discourse/templates/components/d-editor.hbs

@@ -41,6 +41,7 @@
     {{conditional-loading-spinner condition=loading}}
     {{textarea tabindex=tabindex value=value class="d-editor-input" placeholder=placeholderTranslated}}
     {{popup-input-tip validation=validation}}
+    {{plugin-outlet name="after-d-editor" tagName="" args=outletArgs}}
   </div>
 
   <div class="d-editor-preview-wrapper {{if forcePreview 'force-preview'}}">