Fixing typos, creating a WORDLIST, resolving the Roxygen issue, added a condition for minimal Ns for calculating kurtosis and skewness

[sjentsch]

• fixing typos and creating a WORDLIST is the same as before
• the Roxygen error was caused by using #' in functions (e.g., linreg.b.R), this was changed and it now runs with Roxygen 7.2.3
• I made some smaller bug-fixes (corrected T and F to TRUE and FALSE in the examples for descriptives), and added conditions for minimal Ns when calculating kurtosis (N >= 4) and skewness (N >= 3) - there is a comment in the functions why