Add strictPopulate type to PopulateOptions

Added strictPopulate to PopulateOptions, otherwise given option can't be used in TS projects when enforcing types.

Author: Kaljuk

types/index.d.ts

@@ -709,6 +709,8 @@ declare module 'mongoose' {
     model?: string | Model<any>;
     /** optional query options like sort, limit, etc */
     options?: any;
+    /** optional boolean, set to `false` to allow populating paths that aren't in the schema */
+    strictPopulate?: boolean;
     /** deep populate */
     populate?: string | PopulateOptions | (string | PopulateOptions)[];
     /**