Twitchapi

* added Python 3.9 compatibility
* improved example for pubsub

* added new "get channel editors" endpoint
* added new "delete videos" endpoint
* added new "get user block list" endpoint
* added new "block user" endpoint
* added new "unblock user" endpoint
* added new authentication scopes
* some refactoring

* added missing API base url to delete_custom_reward, get_custom_reward, get_custom_reward_redemption and update_redemption_status (thanks asphaltschneider!)

* added option to set a ssl context to be used by Webhook
* fixed modify_channel_information throwing ValueError (thanks asishm!)
* added default route to Webhook on / for easier debugging
* properly check for empty lists in the selection of the used AuthScope in get_users
* raise ValueError if both from_id and to_id are None in subscribe_user_follow of Webhook

* added missing "Create custom rewards" endpoint
* added missing "Delete Custom rewards" endpoint
* added missing "Get Custom Reward" endpoint
* added missing "Get custom reward redemption" endpoint
* added missing "Update custom Reward" endpoint
* added missing "Update redemption status" endpoint
* added missing pagination parameters to endpoints that support them
* improved documentation
* properly handle 401 response after retries

Added a Twitch PubSub client implementation.

* added PubSub client
* made UserAuthenticator URL dynamic
* added named loggers for all modules
* fixed bug in Webhook.subscribe_subscription_events
* added Twitch.get_user_auth_scope