feat(codec/encoder): add time_base accessor

src/codec/encoder/encoder.rs

@@ -123,6 +123,10 @@ impl Encoder {
 		}
 	}
 
+	pub fn time_base(&self) -> Rational {
+		unsafe { Rational::from((*self.as_ptr()).time_base) }
+	}
+
 	pub fn set_time_base<R: Into<Rational>>(&mut self, value: R) {
 		unsafe {
 			(*self.as_mut_ptr()).time_base = value.into().into();