adds more HTML5 characters

adds:
 - [data](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/data)
 - [menuitem](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/menuitem)
 - [main](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/main)
 - [math](https://developer.mozilla.org/en-US/docs/Web/MathML/Element/math)
 - [svg](https://developer.mozilla.org/en-US/docs/Web/SVG/Element/svg)