Add a terminal type of GUI element that lets you append text

[Miles]

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It would be cool to be able to log output to a GUI element by appending lines to the browsers storage instead of trying to keep all the lines in memory on the esp micro.

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Make a way to append text to GUI elements retaining all previous text outside of esp micro memory.

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[Ian Gray]

This would be rather simple to add. I'll bear it in mind for when I'm next working on this.