Multi-time support for exsiting webhooks

[ehsandeep]

Currently, notify doesn't support reusing the same webhook multiple time with different keys/tokens.

For example, if we have the following entry in the config file:-

discord_webhook_url: https://discord.com/api/webhooks/7730624177430/XXXX
discord_username: A
discord: true

discord_webhook_url: https://discord.com/api/webhooks/77306241774308/YYYY
discord_username: B
discord: true

Notify will only post to 2nd discord_webhook_url and the same goes for any other webhook, slack, telegram.

With this support -

For the cases when we want to post the same results on multiple servers/channels, we can simply define the webhook multiple times in config with different values to achieve this.

[ehsandeep]

Related issue - #40