DOC: Added an example for each series.dt field accessor
- [x] xref https://github.com/pandas-dev/pandas/pull/33208#discussion_r402189839
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

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I can also add examples that would cover, ````TimedeltaProperties``` and ```PeriodProperties```, but I think that would be over verbose, wdyt?