feat: add feature for using surf with the h1-client

[danielnelson]

The current Cargo.toml enables default-features for surf which uses surf's curl-client. Since surf contains multiple client backends, the current feature set doesn't provide enough flexibility so that one can use the same HTTP client already in use in other parts of an application.

My project is using the h1-client from surf, and I would like to be able to use just a single HTTP client in my project. This pull request adds a new feature surf-h1 specifically to use surf with the h1-client.

It might be reasonable to also add additional features for surf so that the other clients can be enabled, here is a link to the client features in surf:
https://github.com/http-rs/surf/blob/1ffaba8873d49c672a45442bfd69ca53b81ea1cc/Cargo.toml#L24-L47

[codecov-commenter]

Codecov Report

Merging #357 (94c4793) into master (8909021) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #357   +/-   ##
=======================================
  Coverage   85.17%   85.17%           
=======================================
  Files          68       68           
  Lines        7398     7398           
=======================================
  Hits         6301     6301           
  Misses       1097     1097