DOC: add back google analytics with the new doc theme
WIth the new theme, we didn't have google analytics anymore (how we had it before https://github.com/pandas-dev/pandas/pull/27662), so did a quick PR to add that to the theme with an option: https://github.com/pandas-dev/pydata-bootstrap-sphinx-theme/pull/84
cc @TomAugspurger it's a pitty that I forgot this for the 1.0.0 final release, but so can include it for 1.0.1 Thanks!