feat: update fft/base/fftpack TypeScript declarations

Signed-off-by: stdlib-bot <82920195+stdlib-bot@users.noreply.github.com>

Author: stdlib-bot

lib/node_modules/@stdlib/fft/base/fftpack/docs/types/index.d.ts

@@ -21,6 +21,7 @@
 /* eslint-disable max-lines */
 
 import cffti = require( '@stdlib/fft/base/fftpack/cffti' );
+import cosqi = require( '@stdlib/fft/base/fftpack/cosqi' );
 import decompose = require( '@stdlib/fft/base/fftpack/decompose' );
 import rffti = require( '@stdlib/fft/base/fftpack/rffti' );
 
@@ -62,6 +63,42 @@ interface Namespace {
 	*/
 	cffti: typeof cffti;
 
+	/**
+	* Initializes a workspace array for performing a quarter-wave cosine transform.
+	*
+	* ## Notes
+	*
+	* -   The workspace array should have a length of at least `( 3*N ) + 34` elements.
+	*
+	* @param N - length of the sequence
+	* @param workspace - workspace array
+	* @param strideW - stride length for `workspace`
+	* @param offsetW - starting index for `workspace`
+	* @returns workspace array
+	*
+	* @example
+	* var Float64Array = require( '@stdlib/array/float64' );
+	*
+	* var N = 8;
+	* var workspace = new Float64Array( ( 3*N ) + 34 );
+	*
+	* var out = ns.cosqi( N, workspace, 1, 0 );
+	* // returns <Float64Array>
+	*
+	* var bool = ( out === workspace );
+	* // returns true
+	*
+	* var cosineTable = workspace.slice( 0, N );
+	* // returns <Float64Array>[ ~0.98, ~0.92, ~0.83, ~0.7, ~0.56, ~0.38, ~0.2, ~0.0 ]
+	*
+	* var twiddleFactors = workspace.slice( 2*N, 3*N );
+	* // returns <Float64Array>[ 0, ~0.707, ~0.707, 0, 0, 0, 0, 0 ]
+	*
+	* var factors = workspace.slice( 3*N, ( 3*N ) + 4 );
+	* // returns <Float64Array>[ 8, 2, 2, 4 ]
+	*/
+	cosqi: typeof cosqi;
+
 	/**
 	* Factorizes a sequence length into a product of integers.
 	*