Pushy v0.15.2 - live activities and push-to-talk notifications

[jchambers]

This is a minor release that adds support for live activity notifications and push-to-talk notifications. It also updates a number of dependencies and clarifies documentation around serializing notification payloads to JSON.

For a complete list of changes, please see the v0.15.2 milestone.

---

This discussion was created from the release Pushy v0.15.2 - live activities and push-to-talk notifications.