Fix completion not working for non-HTML files

[absszero]

When adding a new file type to "css.enabledLanguages". Ex.

"css.enabledLanguages": [
    "vue",
    "html"
]

Auto completion only trigger outside HTML attributes . Ex.

<template>
    <a class="text-link"  | ></a>
</template>

It will not trigger within HTML attributes.
(Only works when Vue language extensions are not installed.)

<template>
    <a class="text-link | " ></a>
</template>