Convert Bool and Int tag attributes to specific Html.Attribute functions, rather than the generic `attribute` function

[mbylstra]

Currently for any html attributes that take bools or ints, such as <input readonly=true> or <input tabindex=2>, the generic Html.Attribute.attribute function is used for the conversion. For example, tabindex=2 will be converted to attribute "tabindex" "2" rather than the preferable tabindex 2 from Html.Attribute.tabindex.

For bool attributes, it should be able to handle the absence of an attribute value, such as <input readonly>, and convert that to input [readonly True] []