exclude common instructions

Added

• MECE principle in comment generation
• if failed, assert the error message
• fail-expected argument to fail the test if the expected fail count not correct
• Add a feature to exclude common content of README.md assignment instruction.
  • Common content is marked by the starting marker From here is common to all assignments. and the ending m arker Until here is common to all assignments. in the README.md file, surrounded by double backtick (ascii 96) characters.
• Add start and end markers to mutable code block in the prompt for Gemini.

Changed

• Update license to BSD 3-Clause + Do Not Harm.
• Change the default value of fail-expected to false.
• Improve prompt for Gemini.
  • Add header and footer to the prompt.
  • Modify instruction for failed tests to "Please generate comments mutually exclusive and collectively exhaust ive for the following failed test cases.".
  • Add start and end markers to mutable code block.

Removed

• 'Currently Korean Only' from README.md.