Add `<select/>` tag helper

- #1248

"[Design]" just for missing unit tests. Otherwise complete.
/cc @NTaylorMullen 
:-1: must match the expression for the attribute name. the important thing here is the HTML Boolean semantic -- `attribute-name="attribute-name"`.  if we refactor _and_ add `[HtmlAttributeName]`, a literal `string` would make sense for both expressions.  any other case, no.