* add Catch2 html-renderer

* prefer "contents" instead of "val" for tag contents processing function name html-renderer

* Initial setup for HTML Renderer refactor html-renderer

#129: EnsureVisible function, tabbing to a widget ensures that widget is scrolled 4.x-dev

#23: Panel scrolling method is changed 4.x-dev

#132: List Organizer now honors invisible widgets 4.x-dev

* To<float/double> will no longer cause exceptions 4.x-dev

* IconButton now resizes automatically if no size is given 4.x-dev

#108: Scrolling with arrow keys and page up/down 4.x-dev

#123: Inputlayer ordering issue 4.x-dev

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