apply ckeditor on multiple entities

Apply ckeditor into:

* activity;
* task;
* document;
* accompanying periods

src/Bundle/ChillMainBundle/Resources/public/modules/ckeditor5/index.scss

@@ -1,4 +1,8 @@
 // set min height for ckeditor
 .ck-editor__editable {
     min-height: 150px;
+}
+
+.ck-editor.ck-reset {
+    margin-bottom: 1.5em;
 }