Add documentation for the sendInput command

[lhecker]

sendInput was added in: microsoft/terminal#7249

[opbld33]

Docs Build status updates of commit 93c5e29:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
TerminalDocs/new-terminal-arguments.md	⚠️Warning	View	Details
TerminalDocs/customize-settings/key-bindings.md	✅Succeeded	View

TerminalDocs/new-terminal-arguments.md

• Line 11, Column 1: [Warning-multiple-h1s] Multiple H1s are not allowed. You can only have one top-level heading.
• Line 11, Column 1: [Suggestion-duplicate-h1s] H1 'New Terminal Arguments in the Windows Terminal' is duplicated with other articles: 'new-terminal-arguments.md(11,1), new-terminal-arguments.md(11,1)'. First level headings must be unique within a docset. NOTE: This Suggestion will become a Warning in late September, 2020.

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 in the Docs contributor and Admin Guide
• See the frequently asked questions
• Post your question in the Docs support channel

[DHowett]

/cc @cinnamon-msft gotta make a preview-1.3 branch!