Add "format : color" to Profiles Schema color items

[TheBrain0110]

Summary of the Pull Request

A simple one-liner addition to profiles.schema.json.

Enables VSCode to recognize Color-type entries in profiles.json and show a color decorator in the editor.

"format" : "color" is a nonstandard, VSCode-specific extension to the schema format, but it shouldn't hurt validation for this case.

PR Checklist

• Closes schema: add support for Visual Studio Code color picker #3287
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Validation Steps Performed

Tested manually.

[DHowett-MSFT]

If this schema extension causes VScode to emit an alpha channel, it will be incompatible with the Terminal’s actual schema

[TheBrain0110]

I just tested locally, and while you can use VSCode's color picker to set an alpha value, it gets marked with a warning as being incompatible with the defined schema. So it shouldn't cause any real issues, the warning is right there in the editor.

[DHowett-MSFT]

Sounds great to me

[carlos-zamora]

Thanks for your contribution!!

[carlos-zamora]

/azp run

[azure-pipelines]

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.