mistralai: Add langchain-mistralai partner package (#14783)

Co-authored-by: Chad Phillips <chad@apartmentlines.com>

libs/partners/mistralai/tests/integration_tests/test_compile.py

@@ -0,0 +1,7 @@
+import pytest
+
+
+@pytest.mark.compile
+def test_placeholder() -> None:
+    """Used for compiling integration tests without running any real tests."""
+    pass