Features from optional dependencies

hyper implicit feature

Enables hyper ^0.14

hyper:

A protective and efficient HTTP library for all

Affects ts_opentelemetry_http::hyper

isahc implicit feature

Enables isahc

isahc:

The practical HTTP client that is fun to use

reqwest implicit feature

Enables reqwest ^0.11

reqwest:

higher level HTTP client library

surf implicit feature

Enables surf

surf:

Surf the web - HTTP client framework

Affects ts_opentelemetry_http::surf

tokio implicit feature

Enables tokio

tokio:

An event-driven, non-blocking I/O platform for writing asynchronous I/O backed applications