Add LZ77 dictionary compression (1977)

[artiphishle]

Title: Add LZ77 dictionary compression (1977)

Description:
Implement LZ77, introduced in 1977 by Lempel and Ziv. This algorithm uses a sliding window dictionary and is foundational for modern compressors.

Motivation:
LZ77 introduces dictionary-based compression, enabling discussion of back-references and window sizes.

Requirements:

• Compression / Decompression
• Update README.md

[google-labs-jules]

Jules is on it. When finished, you will see another comment and be able to review a PR.

[google-labs-jules]

Ready for a review! A PR has been created.