yaml2xのリファクタリング

[ma10]

• Move modules required by freee_a11y_gl from requirements.txt to its pyproject.toml.
• Remove redundancy in specifying the default locale values.
• Update the sample config to match the actual defaults.
• Change yaml2x file layout for packaging.
• WIP: make yaml2rst.py a package.
• Adjust pyproject for freee_a11y_gl
• Make packaged yaml2rst work.
• Adjust for packaged yaml2rst.
• yaml2sheet: file layout for converting to a package.
• Turn yaml2sheet into a package.
• Move yaml2sheet into the scripts directory.
• Fix default value settings
• Move freee_a11y_gl to tools/lib
• Update requirements.txt