times method
this × other: this applies first, then o. M cm sets the CTM
to M.times(ctm).
Implementation
PdfContentMatrix times(PdfContentMatrix o) => PdfContentMatrix(
a * o.a + b * o.c,
a * o.b + b * o.d,
c * o.a + d * o.c,
c * o.b + d * o.d,
e * o.a + f * o.c + o.e,
e * o.b + f * o.d + o.f,
);