Implement IF NODE locations

The following Location information has been added This is the information required for parse.y to be a universal parser:

```
❯ ruby --parser=prism --dump=parsetree -y -e "if a; elsif b; else end"
@ ProgramNode (location: (1,0)-(1,23))
+-- locals: []
+-- statements:
    @ StatementsNode (location: (1,0)-(1,23))
    +-- body: (length: 1)
        +-- @ IfNode (location: (1,0)-(1,23))
            +-- if_keyword_loc: (1,0)-(1,2) = "if"
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- predicate:
            |   @ CallNode (location: (1,3)-(1,4))
            |   +-- CallNodeFlags: variable_call, ignore_visibility
            |   +-- receiver: nil
            |   +-- call_operator_loc: nil
            |   +-- name: :a
            |   +-- message_loc: (1,3)-(1,4) = "a"
            |   +-- opening_loc: nil
            |   +-- arguments: nil
            |   +-- closing_loc: nil
            |   +-- block: nil
            +-- then_keyword_loc: nil
            ^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- statements: nil
            +-- subsequent:
            |   @ IfNode (location: (1,6)-(1,23))
            |   +-- if_keyword_loc: (1,6)-(1,11) = "elsif"
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            |   +-- predicate:
            |   |   @ CallNode (location: (1,12)-(1,13))
            |   |   +-- CallNodeFlags: variable_call, ignore_visibility
            |   |   +-- receiver: nil
            |   |   +-- call_operator_loc: nil
            |   |   +-- name: :b
            |   |   +-- message_loc: (1,12)-(1,13) = "b"
            |   |   +-- opening_loc: nil
            |   |   +-- arguments: nil
            |   |   +-- closing_loc: nil
            |   |   +-- block: nil
            |   +-- then_keyword_loc: nil
                ^^^^^^^^^^^^^^^^^^^^^^^^^
            |   +-- statements: nil
            |   +-- subsequent:
            |   |   @ ElseNode (location: (1,15)-(1,23))
            |   |   +-- else_keyword_loc: (1,15)-(1,19) = "else"
            |   |   +-- statements: nil
            |   |   +-- end_keyword_loc: (1,20)-(1,23) = "end"
            |   +-- end_keyword_loc: (1,20)-(1,23) = "end"
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            +-- end_keyword_loc: (1,20)-(1,23) = "end"
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```

0 files changed, 0 insertions, 0 deletions