bump version to 0.2.24

Add description

Add license.

Version bump

- fix MPRIS device_name comparison

- fix discovery mode
- add option to use credentials-only caching
- add rodio backend

v0.2.19

- fix MPRIS 'PlayingStatus' property always returning 'Stopped'

v0.2.18

- fix MPRIS commands triggered a panic
- fix spotifyd not replying to DBus messages
- make spotifyd completely MediaPlayer2 and MediaPlayer2.Player
compatible

- fix help description not filtering possible values for backend,

volume_controller and use-keyring

- fix multiple spotifyd instances cancelling each other out

v0.2.15

- fix a crash when the device name contained special characters