Mlflow-extend

New features
- `log_figure` supports logging of Plotly figure.

Updates
- Bug fix for `log_dict`
- Add `get_or_create_experiment`
- Enhance unit tests
- LightGBM example

New features
- `log_pickle`
- `log_params_flatten`
- `log_metrics_flatten`

Improvements
- Type checking with mypy
- Sort imports with isort

Documentation updates
- Figures for the plotting functions.
- Installation page
- Example page