[FEATURE] API 4.8

[Bibo-Joshi]

Is your feature request related to a problem? Please describe.

API 4.8 support

Pure API changes

• Bot.send_poll: explanation, explanation_parse_mode,
• Poll.{explanation, explanation_entities, open_period, close_date}
• Bot.send_dice: emoji (for whatever reason, sending a 'darts' is considered a die now …
• Dice.emoji

Convenience stuff

• Poll.parse_explanation_entity/ies
• Filters.dice.dice and Filters.dice.darts for filtering only the corresponding emojis. Allow the Filters.dice.*([1, 2]) syntax for both

[Poolitzer]

@Bibo-Joshi Official docs don't mention it, but a bullseye is a 6.

Maybe we should?

[Bibo-Joshi]

Closed by #1917