* Fix: Using the correct discord domain.

* Fix: Using the correct discord domain.

* Docs: Using the correct discord domain.

* Fix: Changed canary and ptb to the new domain.

* Add webhook url overload for DiscordWebhookClient

Adds an overloaded constructor for `DiscordWebhookClient` which accepts the webhook URL. This URL is parsed using a regex for the id and token. If the token is invalid an `ArgumentException` is thrown.

* add null or whitespace check

* add some tests for the new DiscordWebhookClient constructor

* make the Regex static, specify flags

* update regex to look for "discordapp"

* specify reason why exception is thrown despite regex match

* move parsing logic into new function for testing