refactor: improve type declarations for group function using generics

Author: rajutkarsh07

lib/node_modules/@stdlib/utils/group/docs/types/index.d.ts

@@ -51,7 +51,7 @@ interface Options {
 * var out = group( arr, groups );
 * // returns { 'b': [ 'beep', 'boop', 'bar' ], 'f': [ 'foo' ] }
 */
-declare function group( collection: Collection, groups: Collection ): any;
+declare function group<T>( collection: Collection<T>, groups: Collection<T> ): { [key: string]:  Collection<T> };
 
 /**
 * Groups values as arrays associated with distinct keys.
@@ -89,7 +89,7 @@ declare function group( collection: Collection, groups: Collection ): any;
 * var out = group( arr, opts, groups );
 * // returns { 'b': [ [ 0, 'beep' ], [ 1, 'boop' ], [ 3, 'bar' ] ], 'f': [ [ 2, 'foo' ] ] }
 */
-declare function group( collection: Collection, options: Options, groups: Collection ): any;
+declare function group<T>( collection: Collection<T>, options: Options, groups: Collection<T> ): { [key: string]: Collection<T>};
 
 
 // EXPORTS //