perf: improve matrix determinant

Using the rule of Sarrus for 3x3 matrices decreased processing time of
demo_raycast by 60.75%, when rendering 7680x4320 on 16 threads, x86_64.

With rule of Sarrus:	11.780
Without:		30.016

src/matrix.c

@@ -193,6 +193,16 @@ float cray_matrix_determinant(const struct Matrix *a){
     float result = 0;
     if(a->rows == 2 && a->columns == 2){
         result = (a->value[0][0] * a->value[1][1]) - (a->value[0][1] * a->value[1][0]);
+    } else if(a->rows == 3 && a->columns == 3){
+        // rule of Sarrus (3x3 only) https://en.wikipedia.org/wiki/Rule_of_Sarrus
+        result = (
+              a->value[0][0] * a->value[1][1] * a->value[2][2] // +aei
+            + a->value[1][0] * a->value[2][1] * a->value[0][2] // +dhc
+            + a->value[2][0] * a->value[0][1] * a->value[1][2] // +gbf
+            - a->value[2][0] * a->value[1][1] * a->value[0][2] // -gec
+            - a->value[0][0] * a->value[2][1] * a->value[1][2] // -ahf
+            - a->value[1][0] * a->value[0][1] * a->value[2][2] // -dbi
+            );
     } else {
         int row = 0;
         for(int col=0;col<a->columns;col++){