types: add missing $median pipeline stage to aggregation types

Fix Automattic#15209

Author: vkarpov15

test/types/PipelineStage.test.ts

@@ -575,3 +575,12 @@ const vectorSearchStages: PipelineStage[] = [
     }
   }
 ];
+
+function median() {
+  const medianStage: PipelineStage = {
+    $median: {
+      input: ['$test01', '$test02', '$test03'],
+      method: 'approximate'
+    }
+  };
+}

types/pipelinestage.d.ts

@@ -20,6 +20,7 @@ declare module 'mongoose' {
     | PipelineStage.ListSessions
     | PipelineStage.Lookup
     | PipelineStage.Match
+    | PipelineStage.Median
     | PipelineStage.Merge
     | PipelineStage.Out
     | PipelineStage.PlanCacheStats
@@ -187,6 +188,14 @@ declare module 'mongoose' {
       $match: FilterQuery<any>;
     }
 
+    export interface Median {
+      /** [`$median` reference](https://www.mongodb.com/docs/v7.0/reference/operator/aggregation/median/) */
+      $median: {
+        input: number | Expression,
+        method: 'approximate'
+      }
+    }
+
     export interface Merge {
       /** [`$merge` reference](https://www.mongodb.com/docs/manual/reference/operator/aggregation/merge/) */
       $merge: {