Can we use `rustls` instead of `native-tls` by default?

[rinarakaki]

Is your feature request related to a problem? Please describe.

reqwest also uses rustls by default. It's better than having an os-specific installation step.

Describe the solution you'd like

Before:

[features]
default = ["native-tls"]

After:

[features]
default = ["rustls-tls"]