docs: document presence of tls options (#26)

README.md

@@ -167,11 +167,13 @@ Use [`roarr-cli`](https://github.com/gajus/roarr-cli) program to pretty-print th
  * @property environmentVariableNamespace Defines namespace of `HTTP_PROXY`, `HTTPS_PROXY` and `NO_PROXY` environment variables. (Default: `GLOBAL_AGENT_`)
  * @property forceGlobalAgent Forces to use `global-agent` HTTP(S) agent even when request was explicitly constructed with another agent. (Default: `true`)
  * @property socketConnectionTimeout Destroys socket if connection is not established within the timeout. (Default: `60000`)
+ * @property tls `tls.connect()` options.
  */
 type ProxyAgentConfigurationInputType = {|
   +environmentVariableNamespace?: string,
   +forceGlobalAgent?: boolean,
   +socketConnectionTimeout?: number,
+  +tls?: TlsConfigurationType,
 |};
 
 (configurationInput: ProxyAgentConfigurationInputType) => ProxyAgentConfigurationType;