v0.2.1: Core Pipeline Methods and Initial Setup

This is the first major feature release after the initial setup, adding a comprehensive set of core aggregation methods.

✨ Added

• Core Pipeline Methods: Added a wide array of MongoDB aggregation pipeline methods to PipelineBuilder, including: $addFields, $bucket, $bucketAuto, $collStats, $count, $facet, $geoNear, $graphLookup, $indexStats, $lookup, $merge, $out, $redact, $replaceRoot, $replaceWith, $sample, $setWindowFields, $sortByCount, $unionWith, $unset, and $unwind.
• Project Metadata: Added repository, bugs, and homepage links to package.json for better package discovery and support.
• Documentation: Included CONTRIBUTING.md in the npm package files and created the initial CHANGELOG.md.

🔧 Changed

• Improved code organization by alphabetizing the methods in PipelineBuilder.ts.

🐛 Fixed

• Resolved a 404 error for CONTRIBUTING.md on the npm package page.
• Fixed a bug in the sortByCount method implementation.