Lint against tidyverse style guide

[DocEd]

@aasiyahrashan this is great work well done. Some suggestions:
Could I suggest you remove the base R stuff. We agreed a while ago to only teach tidyverse so as to not confuse or overload people.
Also could you run everything through a linter like styler (https://github.com/r-lib/styler) to make sure everything conforms to the tidyverse style guide 👍 (https://style.tidyverse.org/)

[aasiyahrashan]

Done.

The only base R stuff I noticed was the bit where dplyr was contrasted with base R. I removed that, but do you remember noticing anything else?

Thanks.