Fix errors in automated tests

[johnbradley]

Automated tests are failing due to problems running examples. The initial problem is that the functions are not exported in NAMESPACE. I tried adding "colorRampPalette_shuffle" to NAMESPACE and then had the same error for "generate_colors". After adding "generate_colors" there was an error on get_essential:

NoSuchKey (HTTP 404). The specified key does not exist.

I think this is because the environment isn't setup.
Perhaps we shouldn't be testing some of these examples via Github Actions.

Originally posted by @johnbradley in #8 (comment)

[johnbradley]

Initial error seen in automated testing.
https://github.com/matthewhirschey/ddh/actions/runs/4576187679/jobs/8079984562?pr=8#step:6:3217

The error most likely occurred in:
> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: colorRampPalette_shuffle
> ### Title: Function to generate shuffled colors based on 'colorRampPalette'
> ### Aliases: colorRampPalette_shuffle
> 
> ### ** Examples
> 
> colorRampPalette_shuffle(colors = c("#DEBBF4", "#BE34EF", "#AC7B84"))
Error in colorRampPalette_shuffle(colors = c("#DEBBF4", "#BE34EF", "#AC7B84")) : 
  could not find function "colorRampPalette_shuffle"

[johnbradley]

These problems can be reproduced locally within RStudio by running "Build" -> "Check"