func (ms *TransformStack) Push(m mgl64.Mat4) {
	prev := (*ms)[len(*ms)-1]
	(*ms) = append(*ms, prev.Mul4(m))
}
Push multiplies the current top matrix by m, and pushes the result on the
stack.
package matstack
import (
	"errors"
	"fmt"
	"github.com/go-gl/mathgl/mgl64"
)
type TransformStack []mgl64.Mat4
func NewTransformStack() *TransformStack {
	ms := make(TransformStack, 1)
	ms[0] = mgl64.Ident4()
	return &ms
}