SFC structure incorrect edge case

[johnsoncodehk]

Currently use HTMLDocument from vscode-html-languageservice to parse SFC blocks.

Case 1:

'<' in interpolation is detected as start tag.

<template>
{{ '<' }}
</template>

Case 2:

Script code not escape for JS literals.

<script>
'</script>'
// ...
</script>

There are more cases, the above is just to show that the current SFC parser solution is not reliable.

[johnsoncodehk]

We have rollback to @vue/compiler-sfc in #1050.