feat: added text support to system tray for macos, closes #65

[vojty]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• New Binding issue #___
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #___
• No

Checklist

• When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary

Other information

This is just my attempt to finish the work introduced in #369, all credits go to @BenJeau

Tested via RUSTFLAGS='--cfg target_os="macos" --cfg feature="tray"' cargo run --example system_tray

Screen.Recording.2022-09-09.at.9.18.44.mov

[amrbashir]

Thank you for taking this feature to the finish line, just a few nit-picks to go.

[BenJeau]

Thanks @vojty for updating my initial PR and having it merged :)

[vojty]

@BenJeau np, you did the hard work anyway :) However, I didn't realize that we need to expose this new API to tauri as well. Any help here tauri-apps/tauri#5182 would be appreciated.