Fix scala-js#137: TimeRanges start/end type incorrect

Author: mseddon

src/main/scala/org/scalajs/dom/raw/lib.scala

@@ -5076,14 +5076,14 @@ class TimeRanges extends js.Object {
  *
  * MDN
  */
- def start(index: Int): Int = js.native
+ def start(index: Int): Double = js.native
 
  /**
  * Returns the time offset at which a specified time range ends.
  *
  * MDN
  */
- def end(index: Int): Int = js.native
+ def end(index: Int): Double = js.native
 }