test: add user reference matrix

PR-URL: #7895
Reviewed-by: Athan Reines <[email protected]>

Author: ShabiShett07

lib/node_modules/@stdlib/blas/base/ggemm/test/fixtures/column_major_nta_tb.json

@@ -27,6 +27,10 @@
   "offsetB": 0,
   "beta": 1.0,
   "C": [ 1.0, 5.0, 2.0, 6.0, 3.0, 7.0, 4.0, 8.0 ],
+  "C_mat": [
+    [ 1.0, 2.0, 3.0, 4.0 ],
+    [ 5.0, 6.0, 7.0, 8.0 ]
+  ],
   "ldc": 2,
   "strideC1": 1,
   "strideC2": 2,