* add how_to_tune_a_forecaster_model notebook
* modify step1: data preparation
* update based how to train
* modify a bug of summary
* update based on comment
* move to howto
* fix typo
* add file
* update based on comments
* rename the tile
* how to train forecaster
* add a notebook
* add new notebook
* add index
* fix colab link
* change content
Co-authored-by: Xinyi Zhang <xinyi1.zhang@intel.com>
Co-authored-by: theaperdeng <theaperdeng@outlook.com>