parser: Add type for Parser::Source::Range#initialize (#1018)

ref: https://github.com/whitequark/parser/blob/v3.2.2.4/lib/parser/source/range.rb#L37

Author: tk0miya

gems/parser/3.2/parser.rbs

@@ -55,6 +55,7 @@ module Parser
       attr_reader source_buffer: Buffer
       attr_reader begin_pos: Integer
       attr_reader end_pos: Integer
+      def initialize: (Buffer buffer, Integer begin_pos, Integer end_pos) -> void
       def begin: () -> Range
       def end: () -> Range
       def size: () -> Integer