feat: add IsAvailableChanged event to Gw2MumbleService

[Flyga-M]

Adds an IsAvailableChanged event to the Gw2MumbleService. Implemented the same way the other mumble events are implemented.

This is useful for handling the (un)availability of the Gw2MumbleService. With this change, a module can listen to the event instead of regularly checking Gw2MumbleService.IsAvailable.

Remark: When subscribing to the event, the user still has to check Gw2MumbleService.IsAvailable once, because the event only fires when the value changes, regardless of it's value at the time of subscription.

Discussion Reference

All new features must be discussed prior to code review. This is to ensure that the implementation aligns with other design considerations. Please link to the Discord discussion:

https://discord.com/channels/531175899588984842/536970543736291346/1235308611706687529

Is this a breaking change?

Breaking changes require additional review prior to merging. If you answer yes, please explain what breaking changes have been made.

No

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud