Update command-line-arguments.md: Add new --keepOpen parameter to the new-tab options list

[htcfreek]

Add new parameter -keepOpen to new-tab options list.

IMPORTANT:

• Do NOT merge before the PR for the feature implementation is merged: https://github.com/microsoft/terminal/pull/16497
• Do NOT merge before a review form the Terminal project maintainers.

[learn-build-service-prod[bot]]

Learn Build status updates of commit e3364c7:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
TerminalDocs/command-line-arguments.md	:white_check_mark:Succeeded	View

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