Add `to_b` and `to_h` to `JS::Object`

I would like to suggest adding to_b and to_h to JS::Object, to convert into a ruby boolean respective hash.

to_b → boolean
Converts self to true or false:

JS.eval("return true").to_b        # => true
JS.eval("return false").to_b       # => false

to_h → hash
Converts self to a Hash:

JS.eval("return {foo: 'bar'}").to_h         # => { "foo" => "bar" }

将所请求的 JS::Object 方法和 Ruby 示例作为验收标准。首先定位 JS::Object 的实现及其现有的转换行为；然后验证 JavaScript 布尔值会变为 Ruby 布尔值，JavaScript 对象会变为 Ruby Hash，包括示例值。