Path Expansion

File and route paths are expanded.

Plus sign expansion

Append to last non-expanded token.

`@litejs/ui,+/pointer.js,+/svg.js` == `@litejs/ui,@litejs/ui/pointer.js,@litejs/ui/svg.js`

Percent sign expansion

Using the "remove matching suffix pattern" parameter expansion.

Remove shortest match from last non-expanded token end to next char after persent sign and append remaining.

`require="path/a.js,%.css"` == `require="path/a.js,path/a.css"`
`@def settings %.view,%.css` == `@def settings settings.view,settings.css`

@litejs/ui/css/base.css,%/grid.css