* Add DisablePingEveryoneHere/DisablePingRoles/DisablePingUsers keys to config
* Add basic AllowedMentions behavior to discord webhooks
* Initialize b.AllowedMentions on Discord Bridger init
* Call b.getAllowedMentions on each webhook to allow config hot reloading
* Add AllowedMentions on all Discord webhooks/messages
* Add DisablePingEveryoneHere/DisablePingRoles/DisablePingUsers to matterbridge.toml.sample
* Change 'Disable' for 'Allow' and revert logic in Discord AllowedMentions
* Update Discord AllowedMentions in matterbridge.toml.sample
* Fix typo in DisableWebPagePreview
* Replace 'AllowPingEveryoneHere' with 'AllowPingEveryone'
* Replace 3 AllowPingEveryone/Roles/Users bools with an array
* Fix typo