Function: text-scale-set

Set the scale factor of the default face in the current buffer to LEVEL.
If LEVEL is non-zero, `text-scale-mode' is enabled, otherwise it is disabled.

LEVEL is a number of steps, with 0 representing the default size.
Each step scales the height of the default face by the variable
`text-scale-mode-step' (a negative number decreases the height by
the same amount). (fn LEVEL)