Merge pull request #322 from ably/laura/endpoint-doc-string

Add endpoint doc string

Author: lawrence-forooghian

textile/api-docstrings.md

@@ -111,6 +111,7 @@ Passes additional client-specific properties to the REST [`constructor()`]{@link
 | defaultTokenParams: TokenParams? ||| TO3j11 | When a [`TokenParams`]{@link TokenParams} object is provided, it overrides the client library defaults when issuing new Ably Tokens or Ably [`TokenRequest`s]{@link TokenRequest}. |
 | echoMessages: Bool default true ||| RTC1a, TO3h | If `false`, prevents messages originating from this connection being echoed back on the same connection. The default is `true`. |
 | environment: String? ||| RSC15b, TO3k1 | Enables a [custom environment](https://ably.com/docs/platform-customization) to be used with the Ably service. |
+| endpoint: String? ||| REC1b, TO3k8 | Set a routing policy or FQDN to connect to Ably. See [platform customization](https://ably.com/docs/platform-customization). |
 | logHandler: ||| platform specific - TO3c | Controls the log output of the library. This is a function to handle each line of log output. |
 | logLevel: ||| platform specific - TO3b | Controls the verbosity of the logs output from the library. Levels include `verbose`, `debug`, `info`, `warn` and `error`.  |
 | logExceptionReportingUrl: String default "[library specific]" ||| TO3m (deprecated) | DEPRECATED: this property is deprecated and will be removed in a future version. Defaults to a string value for an Ably error reporting DSN (Data Source Name), which is typically a URL in the format `https://[KEY]:[SECRET]@errors.ably.io/[ID]`. When set to `null`, `false` or an empty string (depending on what is idiomatic for the platform), exception reporting is disabled. |