TextStimulus missing font size argument

[musslick]

Sometimes experimenters would like to fit more text on the screen. For that it would be useful to have an argument specifying the font size for the TextStimulus.

Note that the experiment breaks if there is too much text on the screen, e.g.,

  introduction_task = TextStimulus(text='In this experiment, you will be presented with a series of pictures.<br> \
                                       Each picture contains two sets of dots, one left and one right.<br><br> \
                                       You have to indicate whether the two sets contain an equal number of dots \
                                       (press the "y" key for yes) or a different number of dots (press "n" key for no).<br>\
                                       Note: For each picture, you have only 2 seconds to respond, so respond quickly.<br>\
                                       You can only respond with the "y" and "n" keys while the dots are shown.<br><br> \
                                       Press the SPACE key to begin the experiment.', 
                                    choices=[' '])