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: [CmdLineArgs] "--keepOpen" to keep the window/tab/pane open after the process/profile has exited. microsoft/terminal#16497
• Do NOT merge before a review form the Terminal project maintainers.

[learn-build-service-prod]

Learn Build status updates of commit e3364c7:

✅ Validation status: passed

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

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