v0.4 roadmap

[erhant]

• Allow multi-level config with better readability & defaulting, unlike the current single-level config
• Add FFI support for alternative provers (see https://github.com/erhant/circomkit-ffi)
• Fix & use C-tester in macOS (Add support for C witness tester #88)
• Add version command (feat: add version command #99)
• Fix Catch circuit runtime errors in tests #107
• Migrate more examples
• Use tsup