add c and jai

jai/modules/Console_Render/math_extras.jai

@@ -0,0 +1,19 @@
+get_triangle_centroid :: (t: Triangle) -> Vec2s64 {
+    return get_triangle_centroid(t.p1, t.p2, t.p3);
+}
+
+get_triangle_centroid :: (p1: Vec2s64, p2: Vec2s64, p3: Vec2s64) -> Vec2s64 {
+    x := (p1.x + p2.x + p3.x) / 3;
+    y := (p1.y + p2.y + p3.y) / 3;
+
+    return .{x, y};
+}
+
+make_quad_from_rect :: (p1: Vec2s64, p2: Vec2s64) -> Quad {
+    return .{
+        .{ p1.x, p1.y },
+        .{ p2.x, p1.y },
+        .{ p2.x, p2.y },
+        .{ p1.x, p2.y },
+    };
+}