Minimize/optimize package dependencies

• Choose between moments and e1071
  • Only mention e1071 and its alternative measures?
• Session 9
  • Use ggeffects or marginaleffects -- or both? use in more than one session?
• Session 11
  • Replace car with anything that plots scatterplot matrices?
  • Remove corrr entirely?
  • Remove ggcorrplot entirely? (or find a package that does the same, plus scatterplot matrices?)
  • Keep factoextra and ggfortify
  • Find a way to re-use plotly? e.g. https://plotly-r.com/d-charts.html -- or remove entirely
• Session 12
  • Install sf earlier and have a map in Session 3
  • Replace life expectancy example from Session 12 with more complex example?
  • Add a full-fledged network example to justify installing igraph and ggraph?
  • Add a full-fledged dynamic document example using modelsummary (and possibly texreg)?
  • Make pdftools optional (only recommend it in the slides?)
• Extras
  • Provide an additional example using rvest?
  • Keep WDI, but use it more than once? -- see #21
    • Modify exercise-04 to use WDI but save the data
    • Modify life-expectancy to use WDI and save the data

Checks:

• Check that countrycode is used in multiple sessions
• Check that broom is used in multiple sessions
• Check that ggmosaic is used in multiple sessions
• Check that ggrepel is used in multiple sessions, "", "", "",
• Check that performance is used in multiple sessions
• Check that texreg is used in multiple sessions