Feat/Example notebook for the regression models #4413

Job	Run time
docs	11m 39s
lint	1m 5s
tests (macos-latest, 3.9, all)	37m 0s
check-examples (03-FFT-examples.ipynb)	5m 2s
tests (ubuntu-latest, 3.9, all)	38m 37s
check-examples (04-RNN-examples.ipynb)	10m 14s
check-examples (00-quickstart.ipynb)	9m 15s
check-examples (02-data-processing.ipynb)	11m 33s
check-examples (01-multi-time-series-and-covariates.ipynb)	12m 17s
	2h 16m 42s

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