Feature/playable rawdata

Description

Add a raw_data field to Playable to allow retrieving the raw data received via Lavalink. Playable can be constructed with this data.

[x] If code changes were made then they have been tested.
- [x] I have updated the documentation to reflect the changes.
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[ ] This PR fixes an issue.
[x] This PR adds something new (e.g. new method or parameters).
[ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
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