Wavelink

Added Exponential Backoff attempts to `get_tracks`. Retrieving tracks will now by default retry on failure up to a maximum of 5 attempts with an Exponential Backoff.
You can set this to False with the kwarg `retry_on_failure=False`, which will only attempt to retrieve tracks once.

Added support for custom JSON Encoders.

Changed YouTube's Track Image to hqdefault, in place of maxresdefault.

Changes to `Equalizer` which allow for construction without the `build()` classmethod.

Added `name` parameters to the `build()` classmethod and Equalizer constructor to allow setting a custom name.

Added a `name` property to Equalizer. Setting the name should be done by constrcutor or the `build()` classmethod

Added `__str__` and `__repr__` to Equalizer.

Fixed a bug where `set_eq` was setting a blank Equalizer class on the player.

Fixes a bug for AutoSharded bots on discord.py `1.4.0`.

Add heartbeat to node and websocket.

This stabilizes connection to Nodes hosted on a VPS with a router or any such intermediate process that closes the connection if it remains idle.
Which puts the bot in a "reconnection" loop.

Add `player.equalizer` property which allows the user to get the currently applied EQ.

Added `wavelink.WavelinkMixin` to be used in conjunction with a discord.py `commands.Cog`. This class allows for the registration of the new wavelink listeners:

`on_node_ready`
`on_track_start`
`on_track_end`
`on_track_stuck`
`on_track_exception`
`on_websocket_closed`

All listeners must be decorated with the `wavelink.WavelinkMixin.listener()` decorator.
All listeners must be in a `wavelink.WavelinkMixin` class.
Listeners can be stacked.

Docs
---------
[Event Payloads](https://wavelink.readthedocs.io/en/latest/wavelink.html#event-payloads)
[WavelinkMixin](https://wavelink.readthedocs.io/en/latest/wavelink.html#wavelinkmixin)

Example
-----------
py
class Music(commands.Cog, wavelink.WavelinkMixin):

wavelink.WavelinkMixin.listener()
async def on_node_ready(self, node):
print(f'Node {node.identifier} is ready!')