Add column number to the column attributes table

[mbcann01]

Try doing this inside codebook(). Between cb_get_col_attributes() and flextable::flextable()

• [x] Get code working
• [x] Test on README
• [x] Create new screenshots for README
• [x] Update documentation
• [x] devtools::check()
• [x] Update news
• [x] Merge into master
• [x] Commit, push, close

[mbcann01]

Make the column wider

Need to make the column number column wider to accommodate more than 1,000 variables.