Theme Observations from lecture-python-intro

[mmcky]

          Many thanks @AakashGfude and @mmcky,

This looks great! The dark mode is really cool.

I spotted some very minor corner cases that might be improved:

1. For Pandas tables (i.e. the one in long_run_growth) lecture has dark rows that are less visible:

2. The import code is grey, so it looks very similar to the background color, i.e.:

3. Based on my observations, I think graphs are restyled under dark mode (this looks really cool!), but there are some plots that are not in the dark mode (for example, the ones in the inequality lecture)

4. The exercise title is slightly harder to see:
   

5. In Eigenvalues lecture, one of the formulae with special annotations is still in black:

Many thanks in advance.

Originally posted by @HumphreyYang in QuantEcon/lecture-python-intro#311 (comment)