Implement different indicator for calling vs images

[mak448a]

Currently, most of the logic happens in src/main.py. Try separating the main window class into a different file.
Hint: In discord_objects.py, there's a few lines that say this:

# TODO: WORK ON THIS. Make a difference between images and other stuff.
        if not (content := message["content"]):
            content = "[(call/image/other)]"

You can change it by finding what type of content it is based on the message variable.