Support for multiple webhooks.

[versx]

Adds support for multiple webhook endpoints.

Example use is I use a Discord bot and a PokeAlarm instance.

[123FLO321]

maybe rename WEBHOOK to WEBHOOKS

maybe also legacy support for WEBHOOK

try: 
   WEBHOOKS = [WEBHOOK]
except NameError:
   pass

[M4d40]

Better add the string check and transform it if needed to a list.

That way both WEBHOOKS are valid.
A Single one as String and also a List.

(Also that way it is backwards compatible)

[M4d40]

conf_webhook = self.config.WEBHOOK
if isinstance(conf_webhook , str):
    conf_webhook = [conf_webhook ]

for wh in conf_webhook:

[versx]

How about something like this in order to add legacy support? @123FLO321

try:
    webhooks = [self.config.WEBHOOK]
except AttributeError:
    webhooks = self.config.WEBHOOKS

for wh in webhooks:

or

if hasattr(self.config.WEBHOOK, 'property'):