Use icon defined in build.gradle as the taskbar icon (macOs)

[igordmn]

macOs doesn't support icons for individual windows, so when we set icon in singleWindowApplication or in Window, we don't change anything.

To change the icon, we should change it inside build.gradle. It changes the icon for native distribution, but doesn't change it for the debug mode (we have a default java icon).

To fix that, we need to pass this:

jvmArgs("-Xdock:icon=src/jvmMain/resources/ic_launcher.png")

Also, we need to write a warning into the log, if user uses singleWindowApplication(icon= attribute on macOs.

Message in Slack

[igordmn]

Also, we need to write a warning into the log, if user uses singleWindowApplication(icon= attribute on macOs.

Decided not to write warning into the log, as it pollutes the log with unnecessary information. But added more info about [icon] parameter to KDoc