feat: add module mp_units

test/unit_test/static/math_test.cpp

@@ -20,11 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <optional>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>  // IWYU pragma: keep
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <optional>
+#endif
 
 namespace {