feat: getters for Status Code & Data Length
feat: getters for Status Code & Data Length

Implements two methods on `Response` `struct`.

1. `status_code`
2. `data_length`

To act as "Getters" for these private properties in case they
are needed by the client.

frewsxcv/tiny-http,frewsxcv/tiny-http,tiny-http/tiny-http