Handle end-of-file `LineRange`

[simerplaha]

• Resolves #254.

• The issue occurs because FastParse returns an endIndex that exceeds the index of the last character. For example, in the following test code(endIndex) results in IndexOutOfBoundsException because endIndex == code.length.

  In the following case, both endIndex and code.length are equal to 4. But this condition indicates that endIndex spans to the end of the file, which should be handled.

  import fastparse.ScalaWhitespace.whitespace
  import fastparse._
  
  def parser[_: P] =
  P(Index ~~ CharIn("A", "B", "C", "D", "\n").rep(1) ~~ Index)
  
  val code =
  "ABCD" // no newline
  
  val Parsed.Success((startIndex, endIndex), _) =
  fastparse.parse(code, parser(_))
  
  println("startIndex: " + startIndex) // = 0
  println("endIndex: " + endIndex)     // = 4
  println("length: " + code.length)    // = 4
  
  val endIndexChar = code(endIndex) // throws IndexOutOfBoundsException