feat(#52): embed step

[h1alexbel]

In this pull, I've implemented embed step from Method section.

closes #52
History:

• feat(embed step #52): embed sent models
• feat(embed step #52): cohere
• feat(embed step #52): if cohere, test cases
• feat(embed step #52): embed

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PR-Codex overview

This PR adds functionality to generate embeddings for repositories using S-BERT, E5, and Embedv3 models. It also introduces the COHERE_TESTING_TOKEN secret.

Detailed summary

• Added functionality to generate embeddings for repositories using different models
• Introduced COHERE_TESTING_TOKEN secret
• Updated pyproject.toml with dependencies for scikit-learn and cohere
• Updated justfile with new tasks for filtering and extracting data
• Updated README.md with instructions on how to run the new just embed task
• Updated embed.py to handle embedding generation for different models
• Added tests to ensure the generation of embeddings with different models

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