Feat/Example notebook for the regression models #4447

Job	Run time
tests (macos-latest, 3.9, all)	30m 4s
tests (ubuntu-latest, 3.9, all)	29m 40s
docs	10m 29s
lint	1m 12s
check-examples (03-FFT-examples.ipynb)	4m 53s
check-examples (04-RNN-examples.ipynb)	10m 36s
check-examples (00-quickstart.ipynb)	11m 23s
check-examples (02-data-processing.ipynb)	10m 5s
check-examples (01-multi-time-series-and-covariates.ipynb)	12m 6s
	2h 0m 28s

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