[feat] Use ksni crate for tray icons on Linux

[dfaust]

Describe the problem

Currently Tauri uses libappindicator to create tray icons on Linux. But it has far fewer features than the xdg standard, as well as macOS and Windows.
There are multiple bug reports and feature requests regarding tray icon issues on Linux.
In particular it's not possible to handle left clicks and to add tool tips.

Describe the solution you'd like

I would like to use the xdg standard for tray icons, which is supported on all Linux desktop environments and has many more features than libappindicator. Also libappindicator looks pretty dead. The last commit to the src folder is 15 years old.
https://bazaar.launchpad.net/~indicator-applet-developers/libappindicator/trunk/files

It looks to me like https://github.com/iovxw/ksni is a great fit for this task. It should be fairly easy to integrate it into Tauri.

I'm ready to write the necessary code myself. I just want to know if you are interested in merging it and if you would like to keep libappindicator as a choice, or if I can remove it.

Alternatives considered

No response

Additional context

No response

[FabianLars]

Yes, this is desirable, see tauri-apps/tray-icon#107 and tauri-apps/tray-icon#104 for example.

It should be fairly easy to integrate it into Tauri.

Probably yeah, the only thing i'm not sure how to best approach is the inter-op with muda.

[dfaust]

Ok, great. Sounds like you would like to remove libappindicator as well. I'll start working on it then.

[dfaust]

@FabianLars: Integrating it with muda really is a pain. After a few iterations of shoehorning it in, I came up with the following changes. Please have a look at them. If you don't have any major concerns, I will update the docs and create the merge requests.

tauri-apps/tray-icon@dev...dfaust:tray-icon:ksni

tauri-apps/muda@dev...dfaust:muda:ksni

[FabianLars]

Let me pull in @amrbashir the maintainer of the crates in question. I'll still try to take a look myself but i'm still out sick so idk when i can get to it.

[amrbashir]

@dfaust thank you for the hard work, this looks very promising, please feel free to open the PRs and we will discuss the finer details