add a column break into a Word document. A column break is used to add a break in a multi columns section in a Word Document.
This function will be deprecated in the next release because it is not
efficient and make users write complex code, use run_columnbreak()
instead.
slip_in_column_break(x, pos = "before")
an rdocx object
where to add the new element relative to the cursor, "after" or "before".