- Updated all relevant source files to include the new license header.
- Changed the default license in the configuration from MIT to GPL-3.0-or-later.
- Reworked `dcr.toml` handling: added read, validation, and edit through `core::config`
- `new` and `init` use the new config creation logic
- `build` and `run` now require `dcr.toml` and read `compiler` and `name` from it