Document useBackgroundImageForWindow

[carlos-zamora]

Document experimental.useBackgroundImageForWindow from microsoft/terminal#12893

[opbld33]

Docs Build status updates of commit b0cbe1b:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
TerminalDocs/customize-settings/appearance.md	⚠️Warning	View	Details

TerminalDocs/customize-settings/appearance.md

• Line 242, Column 1: [Warning: file-not-found - See documentation] Invalid file link: './../images/background-image-for-window.png'.

For more details, please refer to the build report.

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[carlos-zamora]

@cinnamon-msft two things here...

1. be sure to add the image. It doesn't actually exist. Figured you'd want to get an image/gif for the blog so might as well just throw it in here
2. idk if there's a way to denote experimental settings? It didn't seem like it from the other ones, but figured I'd mention it just in case.

[opbld33]

Docs Build status updates of commit b0cbe1b:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
TerminalDocs/customize-settings/appearance.md	⚠️Warning	View	Details

TerminalDocs/customize-settings/appearance.md

• Line 242, Column 1: [Warning: file-not-found - See documentation] Invalid file link: './../images/background-image-for-window.png'.

For more details, please refer to the build report.

If you see build warnings/errors with permission issues, it might be due to single sign-on (SSO) enabled on Microsoft's GitHub organizations. Please follow instructions here to re-authorize your GitHub account to Docs Build.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

Note: Your PR may contain errors or warnings unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.

For any questions, please:

• Try searching the docs.microsoft.com contributor guides
• Post your question in the Docs support channel