HTable_cell_add_style: Add a style to a cell
In fazetu/htable: Create HTML tables from a data.frame

Add a style to a specific <td> or <th> tag. Changes the styles field.

1 2	obj$cell_add_style(row = NULL, col = NULL, style = NULL, include_header = FALSE)

`row`	Numeric vector of which rows to target.
`col`	Numeric vector of which columns to target.
`style`	Character vector (length 1) of style(s).
`include_header`	Boolean if `rows` should include the header as the 1st index. E.g. if `FALSE`, `row = 1` will target the first row, but if `TRUE`, `row = 1` will target the header.