feat: created fastembed and hybrid dependency groups

[jamescalam]

Fixes #80
Removed fastembed and pinecone-text from the default dependencies and created two dependency groups, [fastembed] and [hybrid]. Installed with:

• fastembed: pip install "semantic-router[fastembed]" or on local pip install ".[fastembed]"
• hybrid: pip install "semantic-router[hybrid]" or on local pip install ".[hybrid]" (note: this is required for HybridRouteLayer

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (1fc9df9) 88.31% compared to head (5006b49) 87.77%.

Files	Patch %	Lines
semantic_router/encoders/bm25.py	50.00%	2 Missing ⚠️
semantic_router/layer.py	50.00%	2 Missing ⚠️
semantic_router/schema.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #81      +/-   ##
==========================================
- Coverage   88.31%   87.77%   -0.55%     
==========================================
  Files          16       16              
  Lines         676      687      +11     
==========================================
+ Hits          597      603       +6     
- Misses         79       84       +5     

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[jamescalam]

Merging, opening issue and another PR for codecov fix