Add icons for supported platforms, discontinued or archived apps, and self-hostable apps.

[InterstellarOne]

I propose adding icons to each service with supported platforms, and the other two options I proposed.
The icons would be for:

• MacOS
• iOS (would replace the current Apple icon)
• Windows (11)
• Linux
• Web
• Discontinued (Could be like a broken chain icon, not sure)
• Self-hostable (maybe a server icon)
• (Android icon could also be updated)

Icons could be sourced from Simple Icons
As well as this, I would suggest adding a legend to explain the meaning of the icons.

(This is a continuation of #410)