Add "Generate Color Theme from Current Setting" command

[sstaub]

Describe the request

Add a "Generate Color Theme from Current Setting" that generates a theme from the currently selected theme, to use as a starting point for making custom VS Code theme extensions.

Additional context

This feature is available when using VS Code:

Additional requests

• https://forum.arduino.cc/t/how-to-get-all-my-1-18-19-libraries-installed-in-2-0-1/1050248/3
• https://forum.arduino.cc/t/arduino-ide-v2-hangs-at-start-up/1030052/9
• https://forum.arduino.cc/t/changing-ide-fonts/1028827
• https://forum.arduino.cc/t/personal-themes/1024606
• https://forum.arduino.cc/t/highlighting-of-errors/1018281/3
• https://forum.arduino.cc/t/high-contrast-theia-theme-changed-and-other-issues/1001842/16
• https://forum.arduino.cc/t/how-to-install-vscode-color-theme-extensions/990374
• Dark mode options arduino-pro-ide#199

Related

• color impossible to change #2582
• theming: support theming customizations through the preferences eclipse-theia/theia#8060

Issue checklist

• I searched for previous requests in the issue tracker
• I verified the feature was still missing when using the latest nightly build
• My request contains all necessary details

[svenefftinge]

Info: VS Code Theme support will land in Theia in December.