[meta] Add comprehensive .github/copilot-instructions.md for better AI code assistance

This comprehensive guide helps GitHub Copilot better understand and navigate the nvm codebase by providing:

- Complete architecture explanation of nvm's POSIX-compliant design across multiple shells
- Detailed mapping of top-level commands to internal functions (install, use, ls, alias, etc.)
- Comprehensive testing infrastructure guide using urchin framework
- Shell environment setup for bash, zsh, dash, sh, and ksh
- CI environment details for GitHub Actions and Travis CI
- shellcheck setup and usage guidelines
- Development best practices for POSIX compliance and multi-shell compatibility
- Windows support via WSL2, Cygwin, and Git Bash
- Complete internal function categorization and debugging techniques

The documentation covers all aspects of the codebase to enable more accurate AI assistance when working with nvm's complex shell script architecture.

.github/workflows/windows-npm.yml

@@ -72,8 +72,11 @@ jobs:
             unset npm_config_prefix
             export NVM_INSTALL_GITHUB_REPO="$NVM_INSTALL_GITHUB_REPO"
             export NVM_INSTALL_VERSION="$NVM_INSTALL_VERSION"
+            export HOME="$(cygpath -u "$USERPROFILE")"
 
+            echo "HOME is $HOME"
             curl -fsSLo- "https://raw.githubusercontent.com/${NVM_INSTALL_GITHUB_REPO}/${NVM_INSTALL_VERSION}/install.sh" | bash
+            ls -l $HOME/.nvm
             . "$HOME/.nvm/nvm.sh"
             nvm install --lts
 

README.md

@@ -150,7 +150,7 @@ RUN touch "${BASH_ENV}"
 RUN echo '. "${BASH_ENV}"' >> ~/.bashrc
 
 # Download and install nvm
-RUN curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.2/install.sh | PROFILE="${BASH_ENV}" bash
+RUN curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | PROFILE="${BASH_ENV}" bash
 RUN echo node > .nvmrc
 RUN nvm install
 ```