Implement more image resizing, fix responsiveness

- Two new image sizes have been added: xl and xxl.
- Image resizing has been implemented in featured images.
- Some elements were not responsive, such as the link preview and code block.

package.json

@@ -30,6 +30,12 @@
             },
             "l": {
                 "width": 1200
+            },
+            "xl": {
+                "width": 1600
+            },
+            "xxl": {
+                "width": 2000
             }
         }
     }