Reorganize and complete vignettes/chk_families.Rmd - "chk Families" docs

[flor14]

This PR:

• Creates new titles ("or families") for chk package functions.
• Adds text and examples to each family
• Adds Advanced R as bibliography

Note: I have used "function input" instead of "function argument" on purpose. In general, we refer to the arguments passed by the user. I think saying "the function argument is a list" could be confusing, as it is not clear whether we are referring to the argument provided or how the function has been defined.

Therefore, I will use "function input" when referring to the argument provided and "function argument" when discussing how the function was designed. I will be consistent with this terminology throughout the documentation.

[flor14]

This PR is probably the most critical. It provides a brief explanation and examples for most of the functions.

• The titles and the way functions are grouped have changed. It is important to notice that there isn’t an organic way to do this. For example, chk_date and chk_date_time, could be part of Scalar Checkers as they were in the previous classification. Now I group them in the category Date Checkers. I tried to focus on what might be useful for a potential user. You may have comments on this.
• Another decision I made was regarding the check_ functions. Initially, I tried to include them in this classification, but after exploring a bit, I realized that they consolidate several of the chk_ functions and seem to follow a different logic than the rest. So I keep them in a separate category. I don't know if there are plans to expand this package, but considering its complexity, check_ functions could eventually be developed into a separate package.
• I also considered classifying the chk_ functions by the type of input. For example, chk_join() can only be applied to data frames. However, this classification seemed less useful for the user.

Once I receive feedback, I will edit this PR if necessary and include the final diagram.

[joethorley]

Looks great to me!