feat: add accumulation and index output policies

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---

Author: kgryte

lib/node_modules/@stdlib/types/index.d.ts

@@ -1597,12 +1597,12 @@ declare module '@stdlib/types/ndarray' {
 	/**
 	* Strict output data type policy.
 	*/
-	type StrictOutputPolicy = 'default' | 'same' | 'promoted' | 'boolean' | 'numeric' | 'real' | 'floating_point' | 'real_floating_point' | 'complex_floating_point' | 'integer' | 'signed_integer' | 'unsigned_integer' | 'accumulation';
+	type StrictOutputPolicy = 'default' | 'default_index' | 'same' | 'promoted' | 'accumulation' | 'boolean' | 'integer_index' | 'boolean_index' | 'mask_index' | 'numeric' | 'real' | 'floating_point' | 'real_floating_point' | 'complex_floating_point' | 'integer' | 'signed_integer' | 'unsigned_integer';
 
 	/**
 	* Output data type policy.
 	*/
-	type OutputPolicy = StrictOutputPolicy | 'boolean_and_generic' | 'numeric_and_generic' | 'real_and_generic' | 'floating_point_and_generic' | 'real_floating_point_and_generic' | 'complex_floating_point_and_generic' | 'integer_and_generic' | 'signed_integer_and_generic' | 'unsigned_integer_and_generic' | 'accumulation_and_generic';
+	type OutputPolicy = StrictOutputPolicy | 'boolean_and_generic' | 'integer_index_and_generic' | 'boolean_index_and_generic' | 'mask_index_and_generic' | 'numeric_and_generic' | 'real_and_generic' | 'floating_point_and_generic' | 'real_floating_point_and_generic' | 'complex_floating_point_and_generic' | 'integer_and_generic' | 'signed_integer_and_generic' | 'unsigned_integer_and_generic';
 
 	/**
 	* Array order.