Add skip_headers argument

[ArtyomKomarenko]

By default returned string contains all headers including auto-generated ['accept', 'accept-encoding', 'connection', 'user-agent', 'content-length']. But these headers are not necessary to execute request by curl in terminal, and sometimes they can obstruct it execution. To avoid that case skip_headers=True can be passed to to_curl method.

[ofw]

Hi! If you think that this change is still relevant please rebase it onto the main branch.

Also I'd suggest to provide the skip_headers param to the to_curl function for any users to be able to skip any list of headers not the hardcoded ones.