Add .editorconfig file for consistent code formatting

[jeremyeder]

Add a standard .editorconfig file to ensure consistent code formatting across different editors and IDEs.

This will help maintain code style consistency and reduce formatting-related diffs in PRs.

The file should include:

• Standard indentation (spaces vs tabs)
• Line endings (LF)
• Character encoding (UTF-8)
• File-specific rules for common file types

This is a simple, low-risk change that improves developer experience.