Add initial version of the action and associated files

[mkardous-silabs]

Description

PR introduces the initial version of the GN build actions and the associated files to maintain the action

• Adds the action.yml that defines the action
• Updates the readme
• Adds vscode settings file
• adds unit test to validate the javascript code
• adds test workflow to validate the whole action
• adds restyler rules and workflow

The git am suggestion for the restyler doesn't work because the default machines don't have configured git configs. This will be in a follow up.

Tests

Unit tests and workflow run