Define AggressiveSplitterPlugin in optimize namespace (#26900)

* Define AggressiveSplitterPlugin in optimize namespace

* Fix lint failures

types/webpack/index.d.ts

@@ -1422,6 +1422,33 @@ declare namespace webpack {
             }
         }
 
+        class AggressiveSplittingPlugin extends Plugin {
+            constructor(options?: AggressiveSplittingPlugin.Options);
+        }
+
+        namespace AggressiveSplittingPlugin {
+            interface Options {
+                /**
+                 * Size in byte.
+                 * Only chunks bigger than the specified minSize are stored in records.
+                 * This ensures the chunks fill up as your application grows,
+                 * instead of creating too many chunks for every change.
+                 *
+                 * Default: 30720
+                 */
+                minSize: 30000;
+                /**
+                 * Size in byte.
+                 * maximum size prefered for each chunk.
+                 *
+                 * Default: 51200
+                 */
+                maxSize: 50000;
+                chunkOverhead: 0;
+                entryChunkMultiplicator: 1;
+            }
+        }
+
         /** @deprecated */
         class DedupePlugin extends Plugin {
             constructor();