add tests and merge origin main

docs/encoders/fastembed.ipynb

docs/encoders/huggingface.ipynb

poetry.lock

pyproject.toml

semantic_router/encoders/__init__.py

semantic_router/encoders/bm25.py

semantic_router/encoders/huggingface.py

semantic_router/hybrid_layer.py

tests/unit/encoders/test_bm25.py

tests/unit/encoders/test_huggingface.py

tests/unit/test_hybrid_layer.py