Add new polls and predictions webhooks.

[FiniteSingularity]

Twitch just announced support in EventSub for the new-ish polls and predictions features. EventSub will now hit webhook endpoints for the following events:

• Poll Begin (https://dev.twitch.tv/docs/eventsub/eventsub-subscription-types#channelpollbegin-beta), fired off when a poll begins. Contains data for the title, choices, bit voting state/cost, and channel point voting state/cost
• Poll Progress (https://dev.twitch.tv/docs/eventsub/eventsub-subscription-types#channelpollprogress-beta), fired of when users vote on a poll. Contains the same data as Poll Begin, but adds the current number of votes, channel point votes, and bit votes for a poll.
• Poll End (https://dev.twitch.tv/docs/eventsub/eventsub-subscription-types#channelpollend-beta), fired off when a poll ends. Contains the same data as Poll Progress, but shows the final votes, channel point votes, and bit votes.
• Prediction Begin (https://dev.twitch.tv/docs/eventsub/eventsub-subscription-types#channelpredictionbegin-beta), fired off when a prediction begins. Contains the title, list of outcomes, and when the prediction is locked.
• Prediction Progress (https://dev.twitch.tv/docs/eventsub/eventsub-subscription-types#channelpredictionprogress-beta), fired off when viewers make predictions. For each outcome, contains the number of users who predicted the outcome, the total channel points bet on the outcome, and the top 10 viewers for each prediction in terms of number of points bet.
• Prediction Lock (https://dev.twitch.tv/docs/eventsub/eventsub-subscription-types#channelpredictionlock-beta), fired off when the prediction is locked and no more channel points can be bet. Same payload as Prediction progress, but the channel points wagered will be the final values.
• Prediction End (https://dev.twitch.tv/docs/eventsub/eventsub-subscription-types#channelpredictionend-beta), fired off when the prediction is either resolved (an outcome is confirmed by the streamer and/or a mod), or the prediction is cancelled. Same payload as Prediction Progress and Lock, but shows the number of bits awarded- null if the result is a refund or a loss, and the number of bits if it is a win.

As many streamers are starting to use the poll and prediction features, these events will be added to TAU. Since the Top Predictors is a bit complex data-wise, I may have to implement a random assignment for the test pane. Such random generation would also be suitable for the Hypetrain event testing, so it would benefit both events.

[FiniteSingularity]

Added with PR #81.