[FEATURE REQUEST]: App tray applet: Add a visual indicator when an app requests activation/xdg-open

[ryanabx]

Cosmic-applets version:

cosmic-applets-1.0.0~alpha.2^git20240924.3670f12-1.fc40.x86_64

Specific applet that this is regarding (if applicable):

app tray

Issue/Bug description:

When an app is activated, a visual indicator should show up implying that something changed in that app. This isn't very well explained, my apologies, but this picture should hopefully help:

Steps to reproduce:

• Open an app that has link sharing, for example discord or element.
• Click a link, which will prompt your web browser of choice to open the link.
• There is no activation indicator, but in other DEs and in windows there would be a visual indicator to imply that the app has received an activation or xdg-open request

Expected behavior:

Other notes: