MAINT: upgrade quantecon-book-theme==0.8.2 (#577)

FIX: FutureWarning in heavy_tails (#581)

* FIX: FutureWarning in heavy_tails

* Update lectures/heavy_tails.md

* minor typo

* fix install of wbgapi

* fix cntry_mapper

[french_rev] review of FutureWarnings (#580)

Tom's edits of typo in french revolution lecture

[greek_square] Fix a minor mistake (#579)

Co-authored-by: Matt McKay <mmcky@users.noreply.github.com>

Change to `np.NAN` --> `np.nan` (#570)

This is deprecated and removed fully in numpy 2.0.

Please see:
https://numpy.org/doc/1.26/reference/constants.html#numpy.NAN

Tom's Feb 4 edits of pv.md lecture in intro series -- corrected answe…

…rs to exercise 4

Tom's edits of tax smoothing lecture, Feb 3

LECT: New Lecture on Tax Smoothing (#568)

* update cons_smooth

* change names

* update text

* add tax_smooth

* update tax smooth lecture

* update lecture

* update tax lecture

* J to W

* update text

* Tom's Jan30 edits of tax-smooth lecture

* update graphs in tax_smooth

* update graphs for cons_smooth

* remove the commented text

* remove capitalization

* Tom's Jan 31 edits of two smoothing lectures

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Co-authored-by: Humphrey Yang <u6474961@anu.edu.au>
Co-authored-by: thomassargent30 <ts43@nyu.edu>
Co-authored-by: Humphrey Yang <39026988+HumphreyYang@users.noreply.github.com>

Tom's edits of pv lecture typo