types: add tsdoc comments re: code review

Author: vkarpov15

types/models.d.ts

@@ -245,6 +245,10 @@ declare module 'mongoose' {
      */
     createCollection<T extends mongodb.Document>(options?: mongodb.CreateCollectionOptions & Pick<SchemaOptions, 'expires'>): Promise<mongodb.Collection<T>>;
 
+    /**
+     * Create an [Atlas search index](https://www.mongodb.com/docs/atlas/atlas-search/create-index/).
+     * This function only works when connected to MongoDB Atlas.
+     */
     createSearchIndex(description: mongodb.SearchIndexDescription): Promise<string>;
 
     /** Connection the model uses. */
@@ -300,6 +304,10 @@ declare module 'mongoose' {
       'deleteOne'
     >;
 
+    /**
+     * Delete an existing [Atlas search index](https://www.mongodb.com/docs/atlas/atlas-search/create-index/) by name.
+     * This function only works when connected to MongoDB Atlas.
+     */
     dropSearchIndex(name: string): Promise<void>;
 
     /**
@@ -477,6 +485,10 @@ declare module 'mongoose' {
       doc: any, options: PopulateOptions | Array<PopulateOptions> | string
     ): Promise<MergeType<THydratedDocumentType, Paths>>;
 
+    /**
+     * Update an existing [Atlas search index](https://www.mongodb.com/docs/atlas/atlas-search/create-index/).
+     * This function only works when connected to MongoDB Atlas.
+     */
     updateSearchIndex(name: string, definition: AnyObject): Promise<void>;
 
     /** Casts and validates the given object against this model's schema, passing the given `context` to custom validators. */