Add SHA-256 hash utility

[Josephat-S]

This pull request enhances the template compilation process in src/generate.js by introducing deduplication to avoid unnecessary file writes and by improving logging to reflect these changes. The main improvements are the addition of a SHA-256 hash comparison to detect unchanged files, and the reporting of both written and skipped files.

Template compilation deduplication and logging improvements:

• Added a sha256 helper function using Node's crypto module to compute file content hashes, enabling detection of unchanged files before writing. [1] [2]
• Updated the template compilation loop to skip writing files whose compiled output matches the existing content, incrementing a skippedCount and logging skipped files in verbose mode.
• Improved summary logging after compilation to show both the number of files written and the number skipped due to no changes.

Closes #87