Add hint about Markdown

views/votes_edit_description.erb

@@ -16,6 +16,7 @@
   <div class="mb-3">
     <label for="description" class="form-label"><%= _("Description") %></label>
     <textarea type="text" name="description" class="form-control"><%= params[:description] %></textarea>
+    <small class="form-text text-muted"><%= _("You can use <a href=\"https://www.markdownguide.org/basic-syntax/\">Markdown</a>.") %></small>
   </div>
   <button type="submit" class="btn btn-primary"><%= _("Save") %></button>
 </form>