Add option for text input boxes to clear when clicked on to edit

[joel4848]

As per title - e.g. an option so that if a text input field has text in already, clicking on it empties the content and places the cursor in there, so that the user can type the new content in without having to manually delete all the existing content first. I think that this is standard behaviour for some text/number input fields you'll encounter on websites etc. and would be a good QoL addition.

Example use case - I have a TIF which the user inputs a number into which updates the linked variable, and then clicks 'set' to run a function based on that value. At the moment when a player needs to input a new number they need to manually delete the number that's already in there first.