The background of the plotter app should be OS (or IDE) theme dependent

[kittaakos]

Describe the problem

When the OS theme is dark and the IDE theme is dark, the plotter app's default background should be dark too. Now it has the default white background color.

To reproduce

• Set the IDE2 theme to dark (or when it's dark by default IDE startup theme based on OS theme #1160),
• Start the monitor,
• Tools > Serial Plotter,
• The plotter loads with a white background color.

plotter-background.mp4

Expected behavior

If the OS theme is dark and/or the IDE theme is dark, the plotter's background is also dark.

Arduino IDE version

7fed8fe

Operating system

macOS

Operating system version

12.3.1

Additional context

No response

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest nightly build
• My report contains all necessary details