Add an instructor note about RStudio previewing colors

[Hao Ye]

How could the content be improved?

RStudio has a feature to preview named and hexadecimal colors. This can distract learners (and instructors) who do not expect it.

Specific Example

The episode that introduces data structures - https://swcarpentry.github.io/r-novice-gapminder/04-data-structures-part1.html

has this code snippet

cats <- data.frame(coat = c("calico", "black", "tabby"),
                    weight = c(2.1, 5.0, 3.2),
                    likes_string = c(1, 0, 1))

Under default settings, RStudio will show the word black with a black background.

Proposed Fix

Per discussion in the slack - https://carpentries.slack.com/archives/C03LE48AY/p1698848972844049

an instructor note would help prepare instructors on this issue, with information about how to disable the feature if desired.

Which part of the content does your suggestion apply to?

https://swcarpentry.github.io/r-novice-gapminder/04-data-structures-part1.html

[Hao Ye]

[PR forthcoming]