test: add failed pug tests

[antfu]

Downstream issue: nuxt/bridge#11

[Shinigami92]

Isn't this theoretically invalid? I think there is a missing v-else.
Currently if the condition would result in false there is no root-element in the component.
Not sure if it is statically analysed that it is always true in given example case.

[antfu]

The problem is that the parser does not understand pug, thus failing to parse <. You are talking about another thing that isn't the scope we should handle.