Added alignable boolean series and its example to `.loc` docs.
- [x] closes #31054
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I'm just not sure if I needed to add `IndexingError` to raises section. Added it to be safe, will remove if it's unnecessary.

Also, when someone uses `df.loc[df['col'] > 0]` it really is the same under the hood, `df['col'] > 0` is a boolean series with an alignable index. So there might be some overlap?