Fix #2694: Make chromadb an optional dependency to fix Windows installation issues

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/storage/test_optional_chromadb.py

@@ -0,0 +1,25 @@
+import unittest
+from unittest.mock import patch, MagicMock
+import sys
+import pytest
+from typing import Any, Dict, List, Optional
+
+
+class TestOptionalChromadb(unittest.TestCase):
+    def test_rag_storage_import_error(self):
+        """Test that RAGStorage raises an ImportError when chromadb is not installed."""
+        with patch.dict(sys.modules, {"chromadb": None}):
+            with pytest.raises(ImportError) as excinfo:
+                from crewai.memory.storage.rag_storage import RAGStorage
+                storage = RAGStorage(type="test")
+            
+            assert "ChromaDB is not installed" in str(excinfo.value)
+
+    def test_knowledge_storage_import_error(self):
+        """Test that KnowledgeStorage raises an ImportError when chromadb is not installed."""
+        with patch.dict(sys.modules, {"chromadb": None}):
+            with pytest.raises(ImportError) as excinfo:
+                from crewai.knowledge.storage.knowledge_storage import KnowledgeStorage
+                storage = KnowledgeStorage()
+            
+            assert "ChromaDB is not installed" in str(excinfo.value)