cli fixes

[BNTFryingPan]

should (hopefully) fix the --extension-api-json option

• added an enum for the host operating system
• new function to get an absolute path from a path relative to the project directory
• 2 new debug commands
  • hxgodot path <path> to test the above function with a path
  • hxgodot pathopt --path=<path> to test the above function with a path from an option. this prevents the shell from resolving ~ on its own
  • usage for all debug commands are now documented in comments
• added a message that appears when you type an invalid command