Extract Grid Style 9 base container with scoping

- Add position and dimensions for Grid Style 9 container
- Use .pp-content-post-grid scoping for isolation

Author: pftg

themes/beaver/assets/css/utilities/components/powerpack/content-grid.css

@@ -216,4 +216,11 @@
 
 .pp-content-post-grid .pp-content-post.pp-grid-style-6 .pp-post-image .pp-content-post-date span {
   display: block;
+}
+
+/* Grid Style 9 Base Container */
+.pp-content-post-grid .pp-content-post.pp-grid-style-9 {
+  position: relative;
+  overflow: hidden;
+  height: 270px;
 }