docs: use vue-html for template examples

[skirtles-code]

Using vue-html for the language of code blocks allows them to highlight Vue template syntax correctly. In particular, directive values are treated as JS expressions, rather than just HTML attributes:

In a few cases I've also changed vue to vue-html. Using vue as the language requires the surrounding <template> tag, otherwise it won't be highlighted correctly. vue-html treats the whole block as template syntax, even without a <template> tag.

It isn't always clear whether an example should be treated as vue-html or html. Some examples are using in-DOM templates and only part of the HTML should be treated as a template. In those few examples I left it as html.

I've made the same changes to the Chinese translation.

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