An indicator icon for the page.
A common use case is an audio or camera indicator in a web browser.
class@TabBar will show it at the beginning of the tab, alongside icon representing property@TabPage:icon or loading spinner.
If the page is pinned, the indicator will be shown instead of icon or spinner.
class@TabOverview will show it at the at the top part of the thumbnail.
property@TabPage:indicator-tooltip can be used to set the tooltip on the indicator icon.
If property@TabPage:indicator-activatable is set to TRUE, the indicator icon can act as a button.
Get indicatorIcon property.