Added TextField input to HTML5 target, could use help!

Hi everyone!

I just merged initial support for TextField input on the HTML5 target (in canvas mode – DOM already worked), but it could use improvements. If anyone is interested, I think that the “__hiddenInput” implementation (could perhaps?) be merged with the “__measureTextWithDOM” DIV, improving the performance of measurements, since we could use the DIV size instead of calling canvas to measure text.

There are also some things about it that might not be perfect – selecting all, for example, or I was not seeing spaces for some reason.

If any kind soul is interested, ping me here, let’s work together in Slack chat, or whatever. This is a good step forward for the HTML5 canvas target (in addition to the recent masking and just tonight, mouse over/out and SimpleButton additions) that continues to make it even stronger, but I don’t want to introduce or undesired performance hits for these new features.

Thanks guys!