Document client_from_env
+/// Constructs a client from the `TELOXIDE_PROXY` environmental variable.
+///
+/// This function passes the value of `TELOXIDE_PROXY` into
+/// [`reqwest::Proxy::all`], if it exists, otherwise returns the default
+/// client.
+///
+/// [`reqwest::Proxy::all`]: https://docs.rs/reqwest/0.10.7/reqwest/struct.Proxy.html#method.all
pub fn client_from_env() -> reqwest::Client {
use reqwest::{Client, Proxy};
