Todo

• Avoid code duplication by unifying subtable.cont and subtable.cat
• Allow user to switch order of summary statistics and category levels
• Catch bad names such as "Total", "p", "Test"
• Add trend tests
• Possibly rework default display for ordered factors
• Allow the user to supply arbitrary Test and CI function
• Add functions to combine / split tables
• Refactor code so that not everything is located in one giant file
• Get Githubactions to properly build pkgdown
• .gitignore unnecessary files
• improve default algorithm to choose significant digits
• finish implementing autolabelling function for SPSS / SAS datasets