You could probably do this by changing all the templates to be all capitals, but that would be fairly tedious.
Another way may be to have a custom Javascript function to output text. There is a function called addText which handles all printing - you could override this function and replace it with a version which capitalises everything.
To do this, you would need to add a Javascript file in the Editor, and call a Javascript function when the game loads. In that function, override addText like this (note - untested!):
window.addText = function(text) {
if (_currentDiv == null) {
createNewDiv("left");
}
_currentDiv.append(text.toUpperCase());
scrollToEnd();
}
Here I've just taken the existing addText function, and changed the _currentDiv.append line to make the text upper case.