Add GPUBackend

tests/test_gpu.cpp

@@ -0,0 +1,10 @@
+#include <catch2/catch_test_macros.hpp>
+#include <trigdx/gpu.hpp>
+
+#include "test_utils.hpp"
+
+TEST_CASE("sinf") { test_sinf<GPUBackend>(1e-1f); }
+
+TEST_CASE("cosf") { test_cosf<GPUBackend>(1e-1f); }
+
+TEST_CASE("sincosf") { test_sincosf<GPUBackend>(1e-1f); }