feat: Add config to disable '_' keybind

[corwinm]

feat: Add config to disable '_' keybind

📝 Description

This PR adds a config option to disable the '_' keybind

🔧 Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• ♻️ Code refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Tests (adding missing tests or correcting existing tests)
• 🎨 Style changes (formatting, missing semi-colons, etc)
• 🔧 Chore (maintenance tasks, dependency updates)
• 🌟 Other (please describe):

🔗 Related Issues

Resolves #49

Testing

• I have tested this change locally
• I have added/updated unit tests
• All existing tests pass

Screenshots (if applicable)

Checklist

• My code follows the project's coding standards
• I have performed a self-review of my code
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have checked my code and corrected any misspellings

Additional Notes

[Copilot]

Pull Request Overview

This PR adds a configuration option to disable the '_' (underscore) keybind that opens the current working directory, allowing users to use the default Vim motion behavior instead.

• Added disableUnderscoreOpenCwd configuration setting with appropriate description
• Implemented conditional keymap registration based on the new setting
• Updated VSCode keybinding conditions to respect the configuration

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/vim/oil.code.lua	Added conditional registration of the '_' keybind based on configuration setting
src/utils/settings.ts	Added getter function for the new configuration option
package.json	Added configuration schema and updated keybinding condition