Fixed [error] Cannot pass a value of type ::Hash[::Symbol, bool] as an argument of type ::String

```
lib/ruby_header_parser/parser.rb:257:58: [error] Cannot pass a value of type `::Hash[::Symbol, bool]` as an argument of type `::String`
│   ::Hash[::Symbol, bool] <: ::String
│     ::Object <: ::String
│       ::BasicObject <: ::String
│
│ Diagnostic ID: Ruby::ArgumentTypeMismatch
│
└       lines = File.open(filepath, "rb") { |f| f.readlines(chomp: true) }
                                                            ~~~~~~~~~~~
```

Author: sue445

sig/non-gemify/io.rbs

@@ -0,0 +1,4 @@
+class IO
+  def readlines: (?String sep, ?Integer limit, ?chomp: bool) -> ::Array[String]
+    | ...
+end