Fix config for Helix rev3 4rows (#10641)

* update "Hardware Availability"

* add a section of "How to build"

* update "Hardware Supported"

* add SPLIT_HAND_MATRIX_GRID_LOW_IS_RIGHT for rev3_4rows/config.h

Co-authored-by: keyaki-namiki <28521374+keyaki-namiki@users.noreply.github.com>

keyboards/helix/rev3_4rows/config.h

@@ -50,6 +50,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 /* Split hand configration */
 #define SPLIT_HAND_MATRIX_GRID D7,B2
+#define SPLIT_HAND_MATRIX_GRID_LOW_IS_RIGHT
 
 /* Dip switch on matrix grid */
 #define DIP_SWITCH_MATRIX_GRID { {0,6}, {1,6}, {5,6}, {6,6} }