drop the first tested release of accessible reference templates for compuitational notebooks.

this first release presents a perceivable, operable, understandable, robust, flexible, assistive, and compromising experience ready jupyter notebooks. the design uses html5 semantic tags to construct a reference annotation object model that provides a good experience on assistive technology. we experiment with settings to configure the reading experience, screen reader experiences. further, we present examples of client accessibility checking for improving the accessibility of authored notebooks.